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Checking an element

Check if an element is included in the array: in_array()

The in_array() function returns a boolean , true if the element value is in the array (not as the key), or false if the element is not present.

$array = ["a", "b", "c"];
$elementToFind= "z";
$inArray = in_array( $elementToFind, $array); // the $elementToFind is NOT in the $array
$elementToFind= "a";
$inArray = in_array( $elementToFind, $array); // the $elementToFind is in the $array

Strict comparison

By default the behaviour is to perform a “loose” comparison. It means true and 1 are considered as “equals”. Why? PHP is the same when you perform a loose comparisons with ==, for example: (true == 1) (is true). If you want a strict comparison you need to use ===, for example (true === 1) (is false). For the in_array() function, you have the third (optional) parameter $strict to define that you want a strict comparison performed. Loose comparison is the default behaviour.

FirstSecondStrict comparisonLoose comparison
1”1”falsetrue
nullarray()falsetrue
true1falsetrue
true”Something”falsetrue

For example

$array = array(
true,
false,
0,
999,
null,
"something"
);
in_array(111, $array); // true, because the first element true
in_array(false, $array); // true
in_array(1, $array); // true because the first element true
in_array('another string', $array); // true , because the first element true
in_array(array(), $array); // true, because the second element false

Case Sensitive

The in_array() function is case sensitive which means "My Test" and "my tesT" are different due to the case of the first character of each string and the last character.

One way to obtain a case insensitive comparison is to use strtolower() “for each element of the array”. This can be handled by the array_map() function. The array_map() function, applies a function to each element of the array. In this case the function is strtolower()

$array = array ("My Test", "second" , "third");
in_array("my tesT", $array);
// false because in_array is case sensitive
in_array(
strtolower("my tesT"),
array_map('strtolower', $array)
); // true