Programming PHP

echo "true!\n";
}
if (array_key_exists('age', $person)) {
echo "exists!\n";
}
exists!
In PHP 4.0.6 and earlier versions, the array_key_exists( ) function was called key_
exists( ). The original name is still retained as an alias for the new name.
Many people use the isset( ) function instead, which returns true if the element
exists and is not NULL:
$a = array(0,NULL,'');
function tf($v) { return $v ? "T" : "F"; }
for ($i=0; $i < 4; $i++) {
printf("%d: %s %s\n", $i, tf(isset($a[$i])), tf(array_key_exists($i, $a)));
}
0: T T
1: F T
2: T T
3: F F
Removing and Inserting Elements in an Array
The array_splice( ) function can remove or insert elements in an array:
$removed = array_splice(array, start [, length [, replacement ] ]);
We’ll look at array_splice( ) using this array:
$subjects = array('physics', 'chem', 'math', 'bio', 'cs', 'drama', 'classics');
We can remove the math, bio, and cs elements by telling array_splice( ) to start at
position 2 and remove 3 elements:
$removed = array_splice($subjects, 2, 3);
// $removed is array('math', 'bio', 'cs')
// $subjects is array('physics', 'chem');
If you omit the length, array_splice( ) removes to the end of the array:
$removed = array_splice($subjects, 2);
// $removed is array('math', 'bio', 'cs', 'drama', 'classics')
// $subjects is array('physics', 'chem');
If you simply want to delete the elements and you don’t care about their values, you
don’t need to assign the results of array_splice( ):
array_splice($subjects, 2);
// $subjects is array('physics', 'chem');
To insert elements where others were removed, use the fourth argument:
$new = array('law', 'business', 'IS');
array_splice($subjects, 4, 3, $new);
// $subjects is array('physics', 'chem', 'math', 'bio', 'law', 'business', 'IS')
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Extracting Multiple Values | 123