How would I go about ordering 1 array into 2 arrays depending on what each part of the array starts with using preg_match() ?
I know how to do this using 1 expression but I don't know how to use 2 expressions.
So far I can have done (don't ask why I'm not using strpos() - I need to use regex):
$gen = array(
'F1',
'BBC450',
'BBC566',
'F2',
'F31',
'SOMETHING123',
'SOMETHING456'
);
$f = array();
$bbc = array();
foreach($gen as $part) {
if(preg_match('/^F/', $part)) {
// Add to F array
array_push($f, $part);
} else if(preg_match('/^BBC/', $part)) {
// Add to BBC array
array_push($bbc, $part);
} else {
// Not F or BBC
}
}
So my question is: is it possible to do this using 1 preg_match() function?
Please ignore the SOMETHING part in the array, it's to show that using just one if else statement wouldn't solve this.
Thanks.
You can use an alternation along with the third argument to preg_match, which contains the part of the regexp that matched.
preg_match('/^(?:F|BBC)/', $part, $match);
switch ($match) {
case 'F':
$f[] = $part;
break;
case 'BBC':
$bbc[] = $part;
break;
default:
// Not F or BBC
}
It is even possible without any loop, switch, or anything else (which is faster and more efficient then the accepted answer's solution).
<?php
preg_match_all("/(?:(^F.*$)|(^BBC.*$))/m", implode(PHP_EOL, $gen), $matches);
$f = isset($matches[1]) ? $matches[1] : array();
$bbc = isset($matches[2]) ? $matches[2] : array();
You can find an interactive explanation of the regular expression at regex101.com which I created for you.
The (not desired) strpos approach is nearly five times faster.
<?php
$c = count($gen);
$f = $bbc = array();
for ($i = 0; $i < $c; ++$i) {
if (strpos($gen[$i], "F") === 0) {
$f[] = $gen[$i];
}
elseif (strpos($gen[$i], "BBC") === 0) {
$bbc[] = $gen[$i];
}
}
Regular expressions are nice, but the are no silver bullet for everything.
Related
There are quite a few questions on SO asking about how to parse a regex pattern and output all possible matches to that pattern. For some reason, though, every single one of them I can find (1, 2, 3, 4, 5, 6, 7, probably more) are either for Java or some variety of C (and just one for JavaScript), and I currently need to do this in PHP.
I’ve Googled to my heart’s (dis)content, but whatever I do, pretty much the only thing that Google gives me is links to the docs for preg_match() and pages about how to use regex, which is the opposite of what I want here.
My regex patterns are all very simple and guaranteed to be finite; the only syntax used is:
[] for character classes
() for subgroups (capturing not required)
| (pipe) for alternative matches within subgroups
? for zero-or-one matches
So an example might be [ct]hun(k|der)(s|ed|ing)? to match all possible forms of the verbs chunk, thunk, chunder and thunder, for a total of sixteen permutations.
Ideally, there’d be a library or tool for PHP which will iterate through (finite) regex patterns and output all possible matches, all ready to go. Does anyone know if such a library/tool already exists?
If not, what is an optimised way to approach making one? This answer for JavaScript is the closest I’ve been able to find to something I should be able to adapt, but unfortunately I just can’t wrap my head around how it actually works, which makes adapting it more tricky. Plus there may well be better ways of doing it in PHP anyway. Some logical pointers as to how the task would best be broken down would be greatly appreciated.
Edit: Since apparently it wasn’t clear how this would look in practice, I am looking for something that will allow this type of input:
$possibleMatches = parseRegexPattern('[ct]hun(k|der)(s|ed|ing)?');
– and printing $possibleMatches should then give something like this (the order of the elements is not important in my case):
Array
(
[0] => chunk
[1] => thunk
[2] => chunks
[3] => thunks
[4] => chunked
[5] => thunked
[6] => chunking
[7] => thunking
[8] => chunder
[9] => thunder
[10] => chunders
[11] => thunders
[12] => chundered
[13] => thundered
[14] => chundering
[15] => thundering
)
Method
You need to strip out the variable patterns; you can use preg_match_all to do this
preg_match_all("/(\[\w+\]|\([\w|]+\))/", '[ct]hun(k|der)(s|ed|ing)?', $matches);
/* Regex:
/(\[\w+\]|\([\w|]+\))/
/ : Pattern delimiter
( : Start of capture group
\[\w+\] : Character class pattern
| : OR operator
\([\w|]+\) : Capture group pattern
) : End of capture group
/ : Pattern delimiter
*/
You can then expand the capture groups to letters or words (depending on type)
$array = str_split($cleanString, 1); // For a character class
$array = explode("|", $cleanString); // For a capture group
Recursively work your way through each $array
Code
function printMatches($pattern, $array, $matchPattern)
{
$currentArray = array_shift($array);
foreach ($currentArray as $option) {
$patternModified = preg_replace($matchPattern, $option, $pattern, 1);
if (!count($array)) {
echo $patternModified, PHP_EOL;
} else {
printMatches($patternModified, $array, $matchPattern);
}
}
}
function prepOptions($matches)
{
foreach ($matches as $match) {
$cleanString = preg_replace("/[\[\]\(\)\?]/", "", $match);
if ($match[0] === "[") {
$array = str_split($cleanString, 1);
} elseif ($match[0] === "(") {
$array = explode("|", $cleanString);
}
if ($match[-1] === "?") {
$array[] = "";
}
$possibilites[] = $array;
}
return $possibilites;
}
$regex = '[ct]hun(k|der)(s|ed|ing)?';
$matchPattern = "/(\[\w+\]|\([\w|]+\))\??/";
preg_match_all($matchPattern, $regex, $matches);
printMatches(
$regex,
prepOptions($matches[0]),
$matchPattern
);
Additional functionality
Expanding nested groups
In use you would put this before the "preg_match_all".
$regex = 'This happen(s|ed) to (be(come)?|hav(e|ing)) test case 1?';
echo preg_replace_callback("/(\(|\|)(\w+)(?:\(([\w\|]+)\)\??)/", function($array){
$output = explode("|", $array[3]);
if ($array[0][-1] === "?") {
$output[] = "";
}
foreach ($output as &$option) {
$option = $array[2] . $option;
}
return $array[1] . implode("|", $output);
}, $regex), PHP_EOL;
Output:
This happen(s|ed) to (become|be|have|having) test case 1?
Matching single letters
The bones of this would be to update the regex:
$matchPattern = "/(?:(\[\w+\]|\([\w|]+\))\??|(\w\?))/";
and add an else to the prepOptions function:
} else {
$array = [$cleanString];
}
Full working example
function printMatches($pattern, $array, $matchPattern)
{
$currentArray = array_shift($array);
foreach ($currentArray as $option) {
$patternModified = preg_replace($matchPattern, $option, $pattern, 1);
if (!count($array)) {
echo $patternModified, PHP_EOL;
} else {
printMatches($patternModified, $array, $matchPattern);
}
}
}
function prepOptions($matches)
{
foreach ($matches as $match) {
$cleanString = preg_replace("/[\[\]\(\)\?]/", "", $match);
if ($match[0] === "[") {
$array = str_split($cleanString, 1);
} elseif ($match[0] === "(") {
$array = explode("|", $cleanString);
} else {
$array = [$cleanString];
}
if ($match[-1] === "?") {
$array[] = "";
}
$possibilites[] = $array;
}
return $possibilites;
}
$regex = 'This happen(s|ed) to (be(come)?|hav(e|ing)) test case 1?';
$matchPattern = "/(?:(\[\w+\]|\([\w|]+\))\??|(\w\?))/";
$regex = preg_replace_callback("/(\(|\|)(\w+)(?:\(([\w\|]+)\)\??)/", function($array){
$output = explode("|", $array[3]);
if ($array[0][-1] === "?") {
$output[] = "";
}
foreach ($output as &$option) {
$option = $array[2] . $option;
}
return $array[1] . implode("|", $output);
}, $regex);
preg_match_all($matchPattern, $regex, $matches);
printMatches(
$regex,
prepOptions($matches[0]),
$matchPattern
);
Output:
This happens to become test case 1
This happens to become test case
This happens to be test case 1
This happens to be test case
This happens to have test case 1
This happens to have test case
This happens to having test case 1
This happens to having test case
This happened to become test case 1
This happened to become test case
This happened to be test case 1
This happened to be test case
This happened to have test case 1
This happened to have test case
This happened to having test case 1
This happened to having test case
I'm facing an issue with a function that gets a string between two other strings.
function string_between($str, $starting_word, $ending_word) {
$subtring_start = strpos($str, $starting_word);
$subtring_start += strlen($starting_word);
foreach ($ending_word as $a){
$size = strpos($str, $a, $subtring_start) - $subtring_start;
}
return substr($str, $subtring_start, $size);
}
The issue is that the function searches for the first ending_word in the array.
An example will be easier to understand:
$array_a = ['the', 'amen']; // Starting strings
$array_b = [',', '.']; // Ending strings
$str = "Hello, the world. Then, it is over.";
Expected result:
"the world."
Current result:
"the world. Then,"
The function will think that the ending_word is "," because it is the first element met in the array_b. However, the text encounters first the '.' after the "the" starting word.
How can I make sure the function goes through the text and stops at the first element in the $str present in the array_b, whatever the position in the array?
Any idea?
Basically, you need to break outside of your foreach loop when $size > 0
That way it stops looping through your array when it finds the 1st occurrence. Here is the more complete code with other fixes:
function stringBetween($string, $startingWords, $endingWords) {
foreach ($startingWords as $startingWord) {
$subtringStart = strpos($string, $startingWord);
if ($subtringStart > 0) {
foreach ($endingWords as $endingWord){
$size = strpos($string, $endingWord, $subtringStart) - $subtringStart + strlen($endingWord);
if ($size > 0) {
break;
}
}
if ($size > 0) {
return substr($string, $subtringStart, $size);
}
}
}
return null;
}
$startArr = array('the', 'amen'); // Starting strings
$endArr = array('.', ','); // Ending strings
$str = "Hello, the world. Then, it is over.";
echo stringBetween($str, $startArr, $endArr); // the world.
This type of problems are best solved by PCRE regexes, only couple of lines needed in function :
function string_between($str, $starts, $ends) {
preg_match("/(?:{$starts}).*?(?:{$ends})/mi", $str, $m);
return $m[0];
}
Then calling like this :
echo string_between("Hello, the world. Then, it is over.", 'the|amen', ',|\.');
Produces : the world.
The trick,- search to the nearest matching ending symbol is done with regex non-greedy seach, indicated by question symbol in pattern .*?. You can even extend this function to accept arrays as starting/ending symbols, just that case modify function (possibly with implode('|',$arr)) for concatenating symbols into regex grouping formula.
Edited version
This works now. Iterate over your teststrings from first array looking for position of occurance from teststring. If found one then search for the second teststring at startposition from end of first string.
To get the shortest hit I store the position from the second and take the minimum.
You can try it at http://sandbox.onlinephpfunctions.com/code/0f1e5c97da62b4daaf0e49f52271fe288d1cacbb
$array_a =array('the','amen');
$array_b =array(',','.', '#');
$str = "Hello, the world. Then, it is over.";
function earchString($str, $array_a, $array_b) {
forEach($array_a as $test) {
$pos = strpos($str, $test);
if ($pos===false) continue;
$found = [];
forEach($array_b as $test2) {
$posStart = $pos+strlen($test);
$pos2 = strpos($str, $test2, $posStart);
$found[] = ($pos2!==false) ? $pos2 : INF;
}
$min = min($found);
if ($min !== INF)
return substr($str,$pos,$min-$pos) .$str[$min];
}
return '';
}
echo earchString($str, $array_a, $array_b);
I have this code:
$getClass = $params->get('pageclass_sfx');
var_dump($getClass); die();
The code above returns this:
string(24) "sl-articulo sl-categoria"
How can I retrieve the specific word I want without mattering its position?
Ive seen people use arrays for this but that would depend on the position (I think) that you enter these strings and these positions may vary.
For example:
$myvalue = $params->get('pageclass_sfx');
$arr = explode(' ',trim($myvalue));
echo $arr[0];
$arr[0] would return: sl-articulo
$arr[1] would return: sl-categoria
Thanks.
You can use substr for that in combination with strpos:
http://nl1.php.net/substr
http://nl1.php.net/strpos
$word = 'sl-categoria';
$page_class_sfx = $params->get('page_class_sfx');
if (false !== ($pos = strpos($page_class_sfx, $word))) {
// stupid because you already have the word... But this is what you request if I understand correctly
echo 'found: ' . substr($page_class_sfx, $pos, strlen($word));
}
Not sure if you want to get a word from the string if you already know the word... You want to know if it's there? false !== strpos($page_class_sfx, $word) would be enough.
If you know exactly what strings you're looking for, then stripos() should be sufficient (or strpos() if you need case-sensitivity). For example:
$myvalue = $params->get('pageclass_sfx');
$pos = stripos($myvalue, "sl-articulo");
if ($pos === FALSE) {
// string "sl-articulo" was not found
} else {
// string "sl-articulo" was found at character position $pos
}
If you need to check if some word are in string you may use preg_match function.
if (preg_match('/some-word/', 'many some-words')) {
echo 'some-word';
}
But this solution can be used for a small list of needed words.
For other cases i suggest you to use some of this.
$myvalue = $params->get('pageclass_sfx');
$arr = explode(' ',trim($myvalue));
$result = array();
foreach($arr as $key=> $value) {
// This will calculates all data in string.
if (!isset($result[$value])) {
$result[$value] = array(); // or 0 if you don`t need to use positions
}
$result[$value][] = $key; // For all positions
// $result[$value] ++; // For count of this word in string
}
// You can just test some words like follow:
if (isset($result['sl-categoria'])) {
var_dump($result['sl-categoria']);
}
I have a PHP array of about 20,000 names, I need to filter through it and remove any name that has the word job, freelance, or project in the name.
Below is what I have started so far, it will cycle through the array and add the cleaned item to build a new clean array. I need help matching the "bad" words though. Please help if you can
$data1 = array('Phillyfreelance' , 'PhillyWebJobs', 'web2project', 'cleanname');
// freelance
// job
// project
$cleanArray = array();
foreach ($data1 as $name) {
# if a term is matched, we remove it from our array
if(preg_match('~\b(freelance|job|project)\b~i',$name)){
echo 'word removed';
}else{
$cleanArray[] = $name;
}
}
Right now it matches a word so if "freelance" is a name in the array it removes that item but if it is something like ImaFreelaner then it does not, I need to remove anything that has the matching words in it at all
A regular expression is not really necessary here — it'd likely be faster to use a few stripos calls. (Performance matters on this level because the search occurs for each of the 20,000 names.)
With array_filter, which only keeps elements in the array for which the callback returns true:
$data1 = array_filter($data1, function($el) {
return stripos($el, 'job') === FALSE
&& stripos($el, 'freelance') === FALSE
&& stripos($el, 'project') === FALSE;
});
Here's a more extensible / maintainable version, where the list of bad words can be loaded from an array rather than having to be explicitly denoted in the code:
$data1 = array_filter($data1, function($el) {
$bad_words = array('job', 'freelance', 'project');
$word_okay = true;
foreach ( $bad_words as $bad_word ) {
if ( stripos($el, $bad_word) !== FALSE ) {
$word_okay = false;
break;
}
}
return $word_okay;
});
I'd be inclined to use the array_filter function and change the regex to not match on word boundaries
$data1 = array('Phillyfreelance' , 'PhillyWebJobs', 'web2project', 'cleanname');
$cleanArray = array_filter($data1, function($w) {
return !preg_match('~(freelance|project|job)~i', $w);
});
Use of the preg_match() function and some regular expressions should do the trick; this is what I came up with and it worked fine on my end:
<?php
$data1=array('JoomlaFreelance','PhillyWebJobs','web2project','cleanname');
$cleanArray=array();
$badWords='/(job|freelance|project)/i';
foreach($data1 as $name) {
if(!preg_match($badWords,$name)) {
$cleanArray[]=$name;
}
}
echo(implode($cleanArray,','));
?>
Which returned:
cleanname
Personally, I would do something like this:
$badWords = ['job', 'freelance', 'project'];
$names = ['JoomlaFreelance', 'PhillyWebJobs', 'web2project', 'cleanname'];
// Escape characters with special meaning in regular expressions.
$quotedBadWords = array_map(function($word) {
return preg_quote($word, '/');
}, $badWords);
// Create the regular expression.
$badWordsRegex = implode('|', $quotedBadWords);
// Filter out any names that match the bad words.
$cleanNames = array_filter($names, function($name) use ($badWordsRegex) {
return preg_match('/' . $badWordsRegex . '/i', $name) === FALSE;
});
This should be what you want:
if (!preg_match('/(freelance|job|project)/i', $name)) {
$cleanArray[] = $name;
}
I was just wondering if PHP has a function that can take a string like 2-1 and produce the arithmetic result of it?
Or will I have to do this manually with explode() to get the values left and right of the arithmetic operator?
I know this question is old, but I came across it last night while searching for something that wasn't quite related, and every single answer here is bad. Not just bad, very bad. The examples I give here will be from a class that I created back in 2005 and spent the past few hours updating for PHP5 because of this question. Other systems do exist, and were around before this question was posted, so it baffles me why every answer here tells you to use eval, when the caution from PHP is:
The eval() language construct is very dangerous because it allows execution of arbitrary PHP code. Its use thus is discouraged. If you have carefully verified that there is no other option than to use this construct, pay special attention not to pass any user provided data into it without properly validating it beforehand.
Before I jump in to the example, the places to get the class I will be using is on either PHPClasses or GitHub. Both the eos.class.php and stack.class.php are required, but can be combined in to the same file.
The reason for using a class like this is that it includes and infix to postfix(RPN) parser, and then an RPN Solver. With these, you never have to use the eval function and open your system up to vulnerabilities. Once you have the classes, the following code is all that is needed to solve a simple (to more complex) equation such as your 2-1 example.
require_once "eos.class.php";
$equation = "2-1";
$eq = new eqEOS();
$result = $eq->solveIF($equation);
That's it! You can use a parser like this for most equations, however complicated and nested without ever having to resort to the 'evil eval'.
Because I really don't want this only only to have my class in it, here are some other options. I am just familiar with my own since I've been using it for 8 years. ^^
Wolfram|Alpha API
Sage
A fairly bad parser
phpdicecalc
Not quite sure what happened to others that I had found previously - came across another one on GitHub before as well, unfortunately I didn't bookmark it, but it was related to large float operations that included a parser as well.
Anyways, I wanted to make sure an answer to solving equations in PHP on here wasn't pointing all future searchers to eval as this was at the top of a google search. ^^
$operation='2-1';
eval("\$value = \"$operation\";");
or
$value=eval("return ($operation);");
This is one of the cases where eval comes in handy:
$expression = '2 - 1';
eval( '$result = (' . $expression . ');' );
echo $result;
You can use BC Math arbitrary precision
echo bcsub(5, 4); // 1
echo bcsub(1.234, 5); // 3
echo bcsub(1.234, 5, 4); // -3.7660
http://www.php.net/manual/en/function.bcsub.php
In this forum someone made it without eval. Maybe you can try it? Credits to them, I just found it.
function calculate_string( $mathString ) {
$mathString = trim($mathString); // trim white spaces
$mathString = ereg_replace ('[^0-9\+-\*\/\(\) ]', '', $mathString); // remove any non-numbers chars; exception for math operators
$compute = create_function("", "return (" . $mathString . ");" );
return 0 + $compute();
}
$string = " (1 + 1) * (2 + 2)";
echo calculate_string($string); // outputs 8
Also see this answer here: Evaluating a string of simple mathematical expressions
Please note this solution does NOT conform to BODMAS, but you can use brackets in your evaluation string to overcome this.
function callback1($m) {
return string_to_math($m[1]);
}
function callback2($n,$m) {
$o=$m[0];
$m[0]=' ';
return $o=='+' ? $n+$m : ($o=='-' ? $n-$m : ($o=='*' ? $n*$m : $n/$m));
}
function string_to_math($s){
while ($s != ($t = preg_replace_callback('/\(([^()]*)\)/','callback1',$s))) $s=$t;
preg_match_all('![-+/*].*?[\d.]+!', "+$s", $m);
return array_reduce($m[0], 'callback2');
}
echo string_to_match('2-1'); //returns 1
As create_function got deprecated and I was utterly needed an alternative lightweight solution of evaluating string as math. After a couple of hours spending, I came up with following. By the way, I did not care about parentheses as I don't need in my case. I just needed something that conform operator precedence correctly.
Update: I have added parentheses support as well. Please check this project Evaluate Math String
function evalAsMath($str) {
$error = false;
$div_mul = false;
$add_sub = false;
$result = 0;
$str = preg_replace('/[^\d\.\+\-\*\/]/i','',$str);
$str = rtrim(trim($str, '/*+'),'-');
if ((strpos($str, '/') !== false || strpos($str, '*') !== false)) {
$div_mul = true;
$operators = array('*','/');
while(!$error && $operators) {
$operator = array_pop($operators);
while($operator && strpos($str, $operator) !== false) {
if ($error) {
break;
}
$regex = '/([\d\.]+)\\'.$operator.'(\-?[\d\.]+)/';
preg_match($regex, $str, $matches);
if (isset($matches[1]) && isset($matches[2])) {
if ($operator=='+') $result = (float)$matches[1] + (float)$matches[2];
if ($operator=='-') $result = (float)$matches[1] - (float)$matches[2];
if ($operator=='*') $result = (float)$matches[1] * (float)$matches[2];
if ($operator=='/') {
if ((float)$matches[2]) {
$result = (float)$matches[1] / (float)$matches[2];
} else {
$error = true;
}
}
$str = preg_replace($regex, $result, $str, 1);
$str = str_replace(array('++','--','-+','+-'), array('+','+','-','-'), $str);
} else {
$error = true;
}
}
}
}
if (!$error && (strpos($str, '+') !== false || strpos($str, '-') !== false)) {
$add_sub = true;
preg_match_all('/([\d\.]+|[\+\-])/', $str, $matches);
if (isset($matches[0])) {
$result = 0;
$operator = '+';
$tokens = $matches[0];
$count = count($tokens);
for ($i=0; $i < $count; $i++) {
if ($tokens[$i] == '+' || $tokens[$i] == '-') {
$operator = $tokens[$i];
} else {
$result = ($operator == '+') ? ($result + (float)$tokens[$i]) : ($result - (float)$tokens[$i]);
}
}
}
}
if (!$error && !$div_mul && !$add_sub) {
$result = (float)$str;
}
return $error ? 0 : $result;
}
Demo: http://sandbox.onlinephpfunctions.com/code/fdffa9652b748ac8c6887d91f9b10fe62366c650
Here is a somewhat verbose bit of code I rolled for another SO question. It does conform to BOMDAS without eval(), but is not equipped to do complex/higher-order/parenthetical expressions. This library-free approach pulls the expression apart and systematically reduces the array of components until all of the operators are removed. It certainly works for your sample expression: 2-1 ;)
preg_match() checks that each operator has a numeric substring on each side.
preg_split() divides the string into an array of alternating numbers and operators.
array_search() finds the index of the targeted operator, while it exists in the array.
array_splice() replaces the operator element and the elements on either side of it with a new element that contains the mathematical result of the three elements removed.
** updated to allow negative numbers **
Code: (Demo)
$expression = "-11+3*1*4/-6-12";
if (!preg_match('~^-?\d*\.?\d+([*/+-]-?\d*\.?\d+)*$~', $expression)) {
echo "invalid expression";
} else {
$components = preg_split('~(?<=\d)([*/+-])~', $expression, 0, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE);
var_export($components); // ['-11','+','3','*','1','*','4','/','-6','-','12']
while (($index = array_search('*',$components)) !== false) {
array_splice($components, $index - 1, 3, $components[$index - 1] * $components[$index + 1]);
var_export($components);
// ['-11','+','3','*','4','/','-6','-','12']
// ['-11','+','12','/','-6','-','12']
}
while (($index = array_search('/', $components)) !== false) {
array_splice($components, $index - 1, 3, $components[$index - 1] / $components[$index + 1]);
var_export($components); // [-'11','+','-2','-','12']
}
while (($index = array_search('+', $components)) !== false) {
array_splice($components, $index - 1, 3, $components[$index - 1] + $components[$index + 1]);
var_export($components); // ['-13','-','12']
}
while (($index = array_search('-', $components)) !== false) {
array_splice($components, $index - 1, 3, $components[$index - 1] - $components[$index + 1]);
var_export($components); // [-25]
}
echo current($components); // -25
}
Here is a demo of the BOMDAS version that uses php's pow() when ^ is encountered between two numbers (positive or negative).
I don't think I'll ever bother writing a version that handles parenthetical expressions ... but we'll see how bored I get.
You can do it by eval function.
Here is how you can do this.
<?php
$exp = "2-1;";
$res = eval("return $exp");
echo $res; // it will return 1
?>
You can use $res anywhere in the code to get the result.
You can use it in form by changing $exp value.
Here is an example of creating a web calculator.
<?php
if (isset($_POST['submit'])) {
$exp = $_POST['calc'];
$res = eval("return $exp;"); //Here we have to add ; after $exp to make a complete code.
echo $res;
}
?>
// html code
<form method="post">
<input type="text" name="calc">
<input type="submit" name="submit">
</form>