I need to get all the positions of a character in a string in a form of an array. I know about the php function strpos() but it does not accept an array as an argument.
This is required:
$name = "australia"; //string that needs to be searched
$positions_to_find_for = "a"; // Find all positions of character "a" in an array
$positions_array = [0,5,8]; // This should be the output that says character "a" comes at positions 0, 5 and 8 in string "australia"
Question: What Loops can help me build a function that can help me achieve the required output?
You can use a for to loop that string:
$name = "australia";
$container = array();
$search = 'a';
for($i=0; $i<strlen($name); $i++){
if($name[$i] == $search) $container[] = $i;
}
print_r($container);
/*
Array
(
[0] => 0
[1] => 5
[2] => 8
)
*/
Codepad Example
No loops necessary
$str = 'australia';
$letter='a';
$letterPositions = array_keys(
array_intersect(
str_split($str),
array($letter)
)
);
var_dump($letterPositions);
Related
What is the most efficient way to count all the occurrences of a specific character in a PHP string?
use this:
echo substr_count("abca", "a"); // will echo 2
Can you not feed the character to preg_match_all?
Not sure what kind of a response you're looking for, but here's a function that might do it:
function findChar($c, $str) {
indexes = array();
for($i=0; $i<strlen($str); $i++) {
if ($str{$i}==$c) $indexes[] = $i;
}
return $indexes;
}
Pass it the character you're looking for and the string you want to look:
$mystring = "She shells out C# code on the sea shore";
$mychar = "s";
$myindexes = $findChar($mychar, $mystring);
print_r($myindexes);
It should give you something like
Array (
[0] => 0
[1] => 4
[2] => 9
[3] => 31
[4] => 35
)
or something...
If you are going to be repeatedly checking the same string, it'd be smart to have some sort of trie or even assoc array for it otherwise, the straightforward way to do it is...
for($i = 0; $i < strlen($s); $i++)
if($s[i] == $c)
echo "{$s[i]} at position $i";
I have the following code:
<?php
$word = "aeagle";
$letter = "e";
$array = strposall($aegle, $letter);
print_r($array);
function strposall($haystack, $needle) {
$occurrence_points = array();
$pos = strpos($haystack, $needle);
if ($pos !== false) {
array_push($occurrence_points, $pos);
}
while ($pos = strpos($haystack, $needle, $pos + 1)) {
array_push($occurrence_points, $pos);
}
return $occurrence_points;
}
?>
As in the example, if I have aegle as my word and I'm searching for e within it, the function should return an array with the values 1 and 4 in it.
What's wrong with my code?
Why not trying instead
$word = "aeagle";
$letter = "e";
$occurrence_points = array_keys(array_intersect(str_split($word), array($letter)));
var_dump($occurrence_points);
I think you're passing the wrong parameters, shouild be $word instead of $aegle
Little bit more literal than the other answer:
function charpos($str, $char) {
$i = 0;
$pos = 0;
$matches = array();
if (strpos($str, $char) === false) {
return false;
}
while (!!$str) {
$pos = strpos($str, $char);
if ($pos === false) {
$str = '';
} else {
$i = $i + $pos;
$str = substr($str, $pos + 1);
array_push($matches, $i++);
}
}
return $matches;
}
https://ignite.io/code/511ff26eec221e0741000000
Using:
$str = 'abc is the place to be heard';
$positions = charpos($str, 'a');
print_r($positions);
while ($positions) {
$i = array_shift($positions);
echo "$i: $str[$i]\n";
}
Which gives:
Array (
[0] => 0
[1] => 13
[2] => 25
)
0: a
13: a
25: a
Other's have pointed out you're passing the wrong parameters. But you're also reinventing the wheel. Take a look at php's regular expression match-all (whoops, had linked the wrong function), it will already return an array of all matches with offsets, when used with the following flag.
flags
flags can be the following flag:
PREG_OFFSET_CAPTURE
If this flag is passed, for every occurring match the appendant string offset will also be returned. Note that this changes the value of matches into an array where every element is an array consisting of the matched string at offset 0 and its string offset into subject at offset 1.
Use a single letter pattern for the search term $letter = '/e/' and you should get back an array with all your positions as the second element of each result array, which you can then finagle into the output format you're looking for.
Update: Jared points out that you do get the capture of the pattern back, but with the flag set, you also get the offset. As a direct answer to the OP's question, try this code:
$word = "aeagle";
$pattern = "/e/";
$matches = array();
preg_match_all($pattern, $word, $matches, PREG_OFFSET_CAPTURE);
print_r($matches);
It has the following ouput:
Array
(
// Matches of the first pattern: /e/
[0] => Array
(
// First match
[0] => Array
(
// Substring of $word that matched
[0] => e
// Offset into $word where previous substring starts
[1] => 1
)
[1] => Array
(
[0] => e
[1] => 5
)
)
)
The results are 3D instead of 2D because preg_match_all can match multiple patterns at once. The hits are for the first (and in this case: only) pattern supplied and are thus in the first array.
And unlike the OP originally stated, 1 and 5 are the correct indexes of the letter e in the string 'aeagle'
aeagle
012345
^ ^
1 5
Performance wise, the customized version of strposall would probably be faster than a regular expression match. But learning to use an in-built function is almost always faster than developing, testing, supporting and maintaining your own code. And 9 times out of 10, that's the most expensive part of programming.
I want to replace all array values with 0 except work and home.
Input:
$array = ['work', 'homework', 'home', 'sky', 'door']
My coding attempt:
$a = str_replace("work", "0", $array);
Expected output:
['work', 0, 'home', 0, 0]
Also my input data is coming from a user submission and the amount of array elements may be very large.
A bit more elegant and shorter solution.
$aArray = array('work','home','sky','door');
foreach($aArray as &$sValue)
{
if ( $sValue!='work' && $sValue!='home' ) $sValue=0;
}
The & operator is a pointer to the particular original string in the array. (instead of a copy of that string)
You can that way assign a new value to the string in the array. The only thing you may not do is anything that may disturb the order in the array, like unset() or key manipulation.
The resulting array of the example above will be
$aArray = array('work','home', 0, 0)
A loop will perform a series of actions many times. So, for each element in your array, you would check if it is equal to the one you want to change and if it is, change it. Also be sure to put quote marks around your strings
//Setup the array of string
$asting = array('work','home','sky','door')
/**
Loop over the array of strings with a counter $i,
Continue doing this until it hits the last element in the array
which will be at count($asting)
*/
for($i = 0; $i < count($asting);$i++){
//Check if the value at the 'ith' element in the array is the one you want to change
//if it is, set the ith element to 0
if ($asting[$i] == 'work' || $asting[$i] == 'home')
$asting[$i] = 0;
}
Here is some suggested reading:
http://www.php.net/manual/en/language.types.array.php
http://www.php.net/manual/en/language.control-structures.php
But if you are struggling on stuff such as looping, you may want to read some introductory programming material. Which should help you really understand what's going on.
A bit other and much quicker way, but true, need a loop:
//Setup the array of string
$asting = array('bar', 'market', 'work', 'home', 'sky', 'door');
//Setup the array of replacings
$replace = array('home', 'work');
//Loop them through str_replace() replacing with 0 or any other value...
foreach ($replace as $val) $asting = str_replace($val, 0, $asting);
//See what results brings:
print_r ($asting);
Will output:
Array
(
[0] => bar
[1] => market
[2] => 0
[3] => 0
[4] => sky
[5] => door
)
An alternative using array_map:
$original = array('work','home','sky','door');
$mapped = array_map(function($i){
$exclude = array('work','home');
return in_array($i, $exclude) ? 0 : $i;
}, $original);
you may try array_walk function:
function zeros(&$value)
{
if ($value != 'home' && $value != 'work'){$value = 0;}
}
$asting = array('work','home','sky','door','march');
array_walk($asting, 'zeros');
print_r($asting);
You can also give array as a parameter 1 and 2 on str_replace...
Just a small point to the for loop. Many dont realize the second comparing task is done every new iteration. So if it was a case of big array or calculation you could optimize loop a bit by doing:
for ($i = 0, $c = count($asting); $i < $c; $i++) {...}
You may also want to see http://php.net/manual/en/function.array-replace.php for original problem unless the code really is final :)
Try This
$your_array = array('work','home','sky','door');
$rep = array('home', 'work');
foreach($rep as $key=>$val){
$key = array_search($val, $your_array);
$your_array[$key] = 0;
}
print_r($your_array);
There are a few techniques on this page that make zero iterated function calls -- which is good performance-wise. For best maintainability, I recommend separating your list of targeted string as a lookup array. By modifying the original array values by reference, you can swiftly replace whole strings and null coalesce non-targeted values to 0.
Code: (Demo)
$array = ['work', 'homework', 'home', 'sky', 'door'];
$keep = ['work', 'home'];
$lookup = array_combine($keep, $keep);
foreach ($array as &$v) {
$v = $lookup[$v] ?? 0;
}
var_export($array);
Output:
array (
0 => 'work',
1 => 0,
2 => 'home',
3 => 0,
4 => 0,
)
You can very easily, cleanly extend your list of targeted strings by merely extending $keep.
If you don't want a classic loop, you can use the same technique without modifying the original array. (Demo)
var_export(
array_map(fn($v) => $lookup[$v] ?? 0, $array)
);
this my final code
//Setup the array of string
$asting = array('work','home','sky','door','march');
/**
Loop over the array of strings with a counter $i,
Continue doing this until it hits the last element in the array
which will be at count($asting)
*/
for($i = 0; $i < count($asting); $i++) {
//Check if the value at the 'ith' element in the array is the one you want to change
//if it is, set the ith element to 0
if ($asting[$i] == 'work') {
$asting[$i] = 20;
} elseif($asting[$i] == 'home'){
$asting[$i] = 30;
}else{
$asting[$i] = 0;
}
echo $asting[$i]."<br><br>";
$total += $asting[$i];
}
echo $total;
I have string:
ABCDEFGHIJK
And I have two arrays of positions in that string that I want to insert different things to.
Array
(
[0] => 0
[1] => 5
)
Array
(
[0] => 7
[1] => 9
)
Which if I decided to add the # character and the = character, it'd produce:
#ABCDE=FG#HI=JK
Is there any way I can do this without a complicated set of substr?
Also, # and = need to be variables that can be of any length, not just one character.
You can use string as array
$str = "ABCDEFGH";
$characters = preg_split('//', $str, -1);
And afterwards you array_splice to insert '#' or '=' to position given by array
Return the array back to string is done by:
$str = implode("",$str);
This works for any number of characters (I am using "#a" and "=b" as the character sequences):
function array_insert($array,$pos,$val)
{
$array2 = array_splice($array,$pos);
$array[] = $val;
$array = array_merge($array,$array2);
return $array;
}
$s = "ABCDEFGHIJK";
$arr = str_split($s);
$arr_add1 = array(0=>0, 1=>5);
$arr_add2 = array(0=>7, 1=>9);
$char1 = '#a';
$char2 = '=b';
$arr = array_insert($arr, $arr_add1[0], $char1);
$arr = array_insert($arr, $arr_add1[1] + strlen($char1), $char2);
$arr = array_insert($arr, $arr_add2[0]+ strlen($char1)+ strlen($char2), $char1);
$arr = array_insert($arr, $arr_add2[1]+ strlen($char1)+ strlen($char2) + strlen($char1), $char2);
$s = implode("", $arr);
print_r($s);
There is an easy function for that: substr_replace. But for this to work, you would have to structure you array differently (which would be more structured anyway), e.g.:
$replacement = array(
0 => '#',
5 => '=',
7 => '#',
9 => '='
);
Then sort the array by keys descending, using krsort:
krsort($replacement);
And then you just need to loop over the array:
$str = "ABCDEFGHIJK";
foreach($replacement as $position => $rep) {
$str = substr_replace($str, $rep, $position, 0);
}
echo $str; // prints #ABCDE=FG#HI=JK
This works by inserting the replacements starting from the end of string. And it would work with any replacement string without having to determine the length of that string.
Working DEMO
Hope you are fine. My question :
In MYSQL i have a table with this type of field
Field Name: TAGS
Value : xavier,celine,marise,leon,john,cathy,polux,maurice
In PHP i do this
$xwords = array();
function array_rpush(&$arr, $item)
{
$arr = array_pad($arr, -(count($arr) + 1), $item);
}
$tags = requete("SELECT tags FROM tbl_tags LIMIT 1;");
while($dtags = mysql_fetch_assoc($tags)){
$words .= array_rpush($xwords, $dtags['tags']);
}
// MY ARRAY XWORDS FOR DEBUG
//
// Array ( [0] => xavier, celine, marise, leon, john, cathy, polux, maurice
//
My script need to find the first letter of each word in this list and check if he match with A / B / C (i create an A-Z index page)
// COUNT $XWORDS VALUE
$total = count($xwords);
// total =1
for($i=0; $i < $total; $i++)
{
$wtags = explode(",",$xwords[$i]);
// wtags = Array ( [0] => xavier [1] => celine [2] => marise... )
while (list($idx,$val) = each($wtags)) {
echo $val{0}."<br>";
echo substr($val,0,1)."<br>";
}
}
echo $val{0}."<br>"; OR echo substr($val,0,1)."<br>" give me just x and nothing after (while give me only the first letter for the first record in array... amazing :))
Perhaps you can help me find a solution. Thanks
The problem with your code is that it generates:
Array ( [0] => "xavier" [1] => " celine" [2] => " marise"... )
So $val[0] = " ". Try to trim($val):
$val = trim($val);
print $val[0];
$sum = array();
foreach($wtags as $tag){
$tag = trim($tag);
empty($sum[$tag{0}]) ? // if we don't have a $sum element for this letter
$sum[$tag{0}] = 1 : // we initialize it
$sum[$tag{0}]++; // else, we sum 1 element to the count.
//$tag{0} is the first letter.
}
// the array $sum has the total of tags under each letter
//
// $sum[x] = 1
// $sum[c] = 2
// $sum[m] = 2
// $sum[l] = 1
// $sum[j] = 1
// $sum[p] = 1