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Last update:   29-10-2021

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Value Exists

Check if a value exists in an array
 
$array = array('a'=>1, 'b'=>2, 'c'=>3);

echo in_array(1, $array); // Output: 1
 
$arr = array ('a' => NULL, 'b' => 2); 

echo isset ($arr['a']); // False 

echo array_key_exists('a', $arr); // True

Array Search

Array search may return false, always use indentical operator.
 
$array = array(1,2,3,4);

echo array_search(4, $array); // Output 3
 
// wrong operator (==)

$array = array(1,2,3,4);

if (array_search(5, $array) == 0) { // true - Look Here

    echo 'Found'; // Output: Found!
}
 
// correct operator (===)

$array = array(1,2,3,4);

if (array_search(5, $array) === 0) { // false - Correct

    echo 'Found'; // Output nothing
}

Keys

If the optional search_value is specified, only the keys for that value are returned.
 
$arr = array('a', 'b', 'a', 'c', 'a', '0', false);

print_r(array_keys($arr)); // [ 0, 1, 2, 3, 4, 5, 6 ]
 
// Search_value provided

$arr = array('a', 'b', 'a', 'c', 'a', '0', false);

print_r(array_keys($arr, 'a')); // [ 0, 2, 4 ]
 
// Strict search (identical comparation)

$arr = array('a', 'b', 'a', 'c', 'a', '0', false);

print_r(array_keys($arr, '0')); // [ 5, 6 ] <span class='exclamation'><b>!</b></span> not true

print_r(array_keys($arr, '0', true)); // [ 5 ] corect

Questions    
Array modify

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