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Regarding if statements in PHP
this is a simple question. But Here I need to know how if condition work with only one variable.
$category='';
if ($category) {
}
can you tell what actually check in If condition? Condition has only one variable..
is it checking variable is TRUE or FALSE?
PHP is a weak typed language. To understand what is evaluated in the if condition, see the conversion rules for booleans.
Quoting from the manual:
When converting to boolean, the following values are considered FALSE:
the boolean FALSE itself
the integer 0 (zero)
the float 0.0 (zero)
the empty string, and the string "0"
an array with zero elements
an object with zero member variables (PHP 4 only)
the special type NULL (including unset variables)
SimpleXML objects created from empty tags
Therefore, your condition will be evaluated as FALSE, since $category == '' and (bool) '' === FALSE
Type 1
$category = '';
if ($category) {
echo 'category';
} else {
echo 'no category';
}
// Output : no category
Type 2
$category = TRUE;
if ($category) {
echo 'category';
} else {
echo 'no category';
}
// Output : category
Type 3
$category = '';
if (!empty($category)) {
echo 'category';
} else {
echo 'no category';
}
// Output : no category
Type 4
$category = 0;
if (!empty($category)) {
echo 'category';
} else {
echo 'no category';
}
// Output : no category
Type 5
$category = 0;
if (isset($category)) {
echo 'category';
} else {
echo 'no category';
}
// Output : category
this will check for TRUE
if ($category) {
}
You empty string will be casted to a boolean value, false in this case. See the manual on Booleans.
This checks whether variable evaluates to true, it's an equivalent of:
if( (bool)$category === true) )
Yes It is checking TRUE or FALSE. If expression evaluates to TRUE, PHP will execute statement, and if it evaluates to FALSE - it'll ignore it.
if ($category) {
}
Will simply check if $category has a value. You did not give $category a value.
In this case, it will give a FALSE.
The block of the if-condition activates whenever the evaluated statement is true.
The empty string in PHP evaluates to false, so this will not be activated. You could be more specific by specifying what you expect, for example:
$category = '';
if (empty($category)) {
}
... in case you expect this to activate whenever it is empty. It really depends on what you are trying to to but like this I assume the condition is never met.
Related
I just started with PHP... This works so far:
$value = get_field( "transmissie" );
if( $value ) {
echo $value;
} else {
echo 'empty';
}
The value variable can be "Manual" or "Automatic"
What I'm trying to do is to check if the value is "Manual" and then I want to echo 'Manual', but if the value is 'Automatic' then I want to echo this:
Automatic
Can someone put me in the right direction? :)
Thanks!
In PHP and many other languages, == is used to test whether two values match. So in your case it's a simple usage of that operator to get what you want:
if( $value == "Manual" ) {
echo $value;
} else {
echo 'Automatic';
}
N.B. If you want to be sure that both values are of the exact same data type then you would use === instead. (e.g. "1" == 1 will return true, because it considers that the string "1" is the same as the integer 1, whereas "1" === 1 will return false - it considers they are not the same because they are not the same data type.)
There's more information in the manual here: https://www.php.net/manual/en/language.operators.comparison.php
I've been working on a very basic search engine. It basically operates by checking if the word exists. If it does, it returns the link. I know most of you would suggest to create a database from phpMyAdmin but I don't remember the password to make the mySql_Connect command work.
Anyway here is the code:
<?php
session_start();
$searchInput = $_POST['search'];
var_dump($inputPage1);
var_dump($searchİnput);
$inputPage1 = $_SESSION['pOneText'];
$inputPage2 = isset($_SESSION['pTwoText']) ? $_SESSION['pTwoText'] : "";
$inputPage3 = isset($_SESSION['pThreeText']) ? $_SESSION['pThreeText'] : "";
if (strpos($inputPage1, $searchInput)) {
echo "True";
} else {
echo "False";
}
?>
When I search a word, any word from any page, weather it exists or not, it always returns false. Does anyone know why?
From the PHP documentation:
Warning: This function may return Boolean FALSE, but may also return a non-Boolean value which evaluates to FALSE. Please read the section on Booleans for more information. Use the === operator for testing the return value of this function.
So the function returns the integer 0 since $searchInput starts at the first character of $inputPage1. Since it is inside an if condition, that expects a boolean, the integer is then converted to one. When converted to boolean, zero is equal to false so instead the else block is executed.
To fix it, you need to use the !== operator (the not equal equivalent of ===):
if (strpos($inputPage1, $searchInput) !== false) {
//...
Try stripos() to match case insensitive
First print all items in $_POST and $_SESSION using
echo "<pre>";
print_r($_POST);
print_r($_SESSION);
and ensure that the search string really exist in the bigger string .
Also make sure that your are using "false" to compare :
i.e
$pos = strpos($biggerString,$seachString);
if($pos !== false)
{
echo "Not found";
}
This question already has answers here:
Why check both isset() and !empty()
(10 answers)
Closed 12 months ago.
When coding php I try to avoid as many warnings as possible. There is one question that bugs me for quite some time now, regarding arrays.
When working with arrays and their values I often check for empty values first before I go to the "real work".
if(array_key_exists('bla', $array){
if( !empty($array['bla']) {
# do something
}
}
My Question is:
This is a lot of code for just checking if I have values to work with. Is there some shorter way to check a value within an array that may or may not exist?
Don't use empty unless you are sure that's what you want:
Returns FALSE if var exists and has a non-empty, non-zero value. Otherwise returns TRUE.
The following things are considered to be empty:
"" (an empty string)
0 (0 as an integer)
0.0 (0 as a float)
"0" (0 as a string)
NULL
FALSE
array() (an empty array)
$var; (a variable declared, but without a value)
The manual doesn't explicitly list the "if var doesn't exist" cases, but here are a couple:
$array['undeclaredKey'] (an existing array, but key not declared)
$undeclaredVar; (a variable not declared)
Usually the array_key_exists check should suffice.
If you are checking for a non-empty value, then you can just use !empty($array['bla']).
You can also use isset($array['bla']), which returns false when: 1) key is not defined OR 2) if the value stored for the key is null. The only foolproof way to check if the array contains a key (even if its value is null) is to use array_key_exists().
The call to empty() is safe even if the key exists (behaves like isset()), so you don't have to protect it by the array_key_exists().
I am surprised this was not mentioned, but the shortest way fetch a value for a key without generating a warning/error is using the Error Control Operator:
// safely fetch from array, will return NULL when key doesn't exist
$value = #$array['bla'];
This allows you get the value for any key with the possibilty of its return value being null if the key does not exist.
You can simply do
if (!empty($array['bla']) {
# do something
}
I use that all the time in drupal and is good way to check if is available and avoid any kind of warnings.
Just do:
if (!empty($array['bla'])) {
There will be no warning if the key doesn't exist.
Not sure why no one mentioned isset yet, but you could do something like this:
// Before
if(array_key_exists('bla', $array){
if( !empty($array['bla']) {
// After (if element of array is scalar)
// Avoids warning and allows for values such as 0
if ((true === isset($array['bla'])) && (mb_strlen($array['bla']) > 0)) {
// After (if element of array is another array
// Avoids warning and ensures element is populated
if ((true === isset($array['bla'])) && (count($array['bla']) > 0)) {
If you really want to get crazy with a better way of checking vars, you could create a standardized API, below are a few methods I created to avoid laundry list function calls for variable checking:
class MyString
{
public static function populated($string)
{
//-----
// Handle various datatypes
//-----
// Don't want to assume an array as a string, even if we serialize then check
if (is_array($string)) {
return false;
}
if (is_object($string)) {
if (!is_callable(array($string, '__toString'))) {
return false;
}
$string = (string) $string;
}
//-----
return (mb_strlen($string) > 0) ? true : false;
}
}
class MyArray
{
public static function populatedKey($key, $array, $specificValue = null, $strict = true)
{
if ((is_array($array)) &&
(array_key_exists($key, $array))) {
if (is_array($array[$key])) {
return (count($array[$key]) > 0) ? true : false;
}
elseif (is_object($array[$key])) {
return true;
}
elseif (mb_strlen($array[$key]) > 0) {
if (!is_null($specificValue)) {
if ($strict === true) {
return ($array[$key] === $specificValue) ? true : false;
} else {
return ($array[$key] == $specificValue) ? true : false;
}
}
return true;
}
}
return false;
}
}
// Now you can simplify calls
if (true === MyArray::populatedKey('bla', $array)) { // Do stuff }
if (true === MyString::populated($someString)) { // Do stuff }
There are 1K ways to skin a cat, but standardizing calls like this increase Rapid Application Development (RAD) quite a bit, keeps the calling code clean, and helps with self documentation (semantically logical).
This question already has answers here:
How to check whether an array is empty using PHP?
(24 answers)
Closed 7 years ago.
I have the following code
<?php
$error = array();
$error['something'] = false;
$error['somethingelse'] = false;
if (!empty($error))
{
echo 'Error';
}
else
{
echo 'No errors';
}
?>
However, empty($error) still returns true, even though nothing is set.
What's not right?
There are two elements in array and this definitely doesn't mean that array is empty. As a quick workaround you can do following:
$errors = array_filter($errors);
if (!empty($errors)) {
}
array_filter() function's default behavior will remove all values from array which are equal to null, 0, '' or false.
Otherwise in your particular case empty() construct will always return true if there is at least one element even with "empty" value.
You can also check it by doing.
if(count($array) > 0)
{
echo 'Error';
}
else
{
echo 'No Error';
}
Try to check it's size with sizeof if 0 no elements.
PHP's built-in empty() function checks to see whether the variable is empty, null, false, or a representation of zero. It doesn't return true just because the value associated with an array entry is false, in this case the array has actual elements in it and that's all that's evaluated.
If you'd like to check whether a particular error condition is set to true in an associative array, you can use the array_keys() function to filter the keys that have their value set to true.
$set_errors = array_keys( $errors, true );
You can then use the empty() function to check whether this array is empty, simultaneously telling you whether there are errors and also which errors have occurred.
array with zero elements converts to false
http://php.net/manual/en/language.types.boolean.php
However, empty($error) still returns true, even though nothing is set.
That's not how empty() works. According to the manual, it will return true on an empty array only. Anything else wouldn't make sense.
From the PHP-documentation:
Returns FALSE if var has a non-empty and non-zero value.
The following things are considered to be empty:
"" (an empty string)
0 (0 as an integer)
0.0 (0 as a float)
"0" (0 as a string)
NULL
FALSE
array() (an empty array)
var $var; (a variable declared, but without a value in a class)
function empty() does not work for testing empty arrays!
example:
$a=array("","");
if(empty($a)) echo "empty";
else echo "not empty"; //this case is true
a function is necessary:
function is_array_empty($a){
foreach($a as $elm)
if(!empty($elm)) return false;
return true;
}
ok, this is a very old question :) , but i found this thread searching for a solution and i didnt find a good one.
bye
(sorry for my english)
hi array is one object so it null type or blank
<?php
if($error!=null)
echo "array is blank or null or not array";
//OR
if(!empty($error))
echo "array is blank or null or not array";
//OR
if(is_array($error))
echo "array is blank or null or not array";
?>
I can't replicate that (php 5.3.6):
php > $error = array();
php > $error['something'] = false;
php > $error['somethingelse'] = false;
php > var_dump(empty($error));
bool(false)
php > $error = array();
php > var_dump(empty($error));
bool(true)
php >
exactly where are you doing the empty() call that returns true?
<?php
if(empty($myarray))
echo"true";
else
echo "false";
?>
In PHP, even if the individual items within an array or properties of an object are empty, the array or object will not evaluate to empty using the empty($subject) function. In other words, cobbling together a bunch of data that individually tests as "empty" creates a composite that is non-empty.
Use the following PHP function to determine if the items in an array or properties of an object are empty:
function functionallyEmpty($o)
{
if (empty($o)) return true;
else if (is_numeric($o)) return false;
else if (is_string($o)) return !strlen(trim($o));
else if (is_object($o)) return functionallyEmpty((array)$o);
// If it's an array!
foreach($o as $element)
if (functionallyEmpty($element)) continue;
else return false;
// all good.
return true;
}
Example Usage:
$subject = array('', '', '');
empty($subject); // returns false
functionallyEmpty($subject); // returns true
class $Subject {
a => '',
b => array()
}
$theSubject = new Subject();
empty($theSubject); // returns false
functionallyEmpty($theSubject); // returns true
I want to check if a query variable exists or not. Then I would do something based on that query value. If it exists and is true, do something. If it doesn't exist or is false, do something else such as show a 404 page.
e.g If the url was domain.com?konami=true
if (condition) {
//something
} else {
//show404
}
OPs question is a bit unclear. If you assume that he wants to check that konami is a $_GET parameter and that it has the value of "true" do:
if (isset($_GET["konami"]) === true && $_GET["konami"] === "true") {
// something
} else {
// show 404
}
The problem with the current accepted answer (by Cameron) is that it's lacking the isset check (which is unforgivable, it is objectively wrong). The problem of the highest voted answer (by Jan Hancic) is that it lacks the === "true" check (which is debatable, it depends on how your interpret the question).
Note that && is a lazy-and, meaning that if the first part is false, the second part will never be evaluated, which prevents the "Undefined index" warning. So the order of the statements is important.
Also note that $a === true is not the same as $a === "true". The first compares a boolean whereas the second compares a string.
If you do weak comparison $a == true you are checking for truthy-ness.
Many values are truthy, like the string "true", the number 1, and the string "foo".
Examples of falsy values are: empty string "", the number 0 and null.
"true" == true; // true
"foo" == true; // true
1 == true; // true
"" == true; // false
0 == true; // false
null == true; // false
"true" === true; // false
"true" === false; // false
There is a little confusion around what value should be tested. Do you want to test the konami parameter for being true in the sense of boolean, i.e. you want to test konami parameter for being truthy, or do you want to test if it has string value equal to "true"? Or do you want to test konami parameter for any value in general?
I guess what is wanted here is to test konami for a given string value, "true" in this case, and for being set at the same time. In this case, this is perfectly enough:
ini_set('error_reporting', E_ALL & ~E_NOTICE);
...
if ($_GET['konami'] == "true")
...
This is enough, because if the $_GET['konami'] is unset, it cannot be equal to any string value except for "". Using === is not neccessary since you know that $_GET['konami'] is string.
Note that I turn off the E_NOTICE which someone may not like - but these type of "notices" are normally fine in many programming languages and you won't miss anything if you disable them. If you don't, you have to make your code unecessarily complex like this:
if (isset($_GET['konami']) && $_GET['konami'] == "true")
Do you really want to complicate your code with this, or rather make it simple and ignore the notices like Undefinex index? It's up to you.
Problems with other answers as you mentioned:
#Jan Hancic answer: it tests for true, not "true".
#Cameron answer: might be simplified and he didn't mention the necessity of disabling E_NOTICE.
#Frits van Campen's answer: too complex to my taste, unnecessary test for === true
Umm this?
if (isset($_GET['konami']) === true) {
// something
} else {
//show 404
}
Easy:
if(isset($_GET['konami']) && $_GET['konami'] != 'false') {
//something
} else {
// 404
}
quick and simple.
$konami = filter_input(INPUT_GET, 'konami', FILTER_VALIDATE_BOOLEAN) or die();
ref:
filter flags
filter_input
You may try this code. In this code checked two conditions by one if condition that is $konami contains value and $konami contains 'true'.
$konami = $_GET['konami'];
if( ($konami) && ($konami == "true")){
/*enter you true statement code */
}else {
/* enter your false statement code */
}
You can do it like this:
$konami = false;
if(isset($_GET['konami'])){
$konami = $_GET['konami'];
}
if($konami == "true"){
echo 'Hello World!';
}
else{
header('HTTP/1.0 404 Not Found');
}
In this case you'll always have $konami defined and - if set - filled with the value of your GET-parameter.
if(!$variable) {
//the variable is null
die("error, $variable is null");
}else{
//the variable is set, your code here.
$db->query("....");
}
This works best:
$konami = $_GET['konami'];
if($konami == "true")
{
echo 'Hello World!';
}
else
{
header('HTTP/1.0 404 Not Found');
}
Easiest and shortest way of doing it:
if($konami != null){ echo $konami; } else { header('HTTP/1.0 404 Not Found'); }