Php foreach add to array with key

Question

foreach() will handle the array you pass into it as a static structure, it can't be dynamic as far as the number of iterations go. You can change the values by passing the value of the iteration by reference (&$value) but you can't add new ones in the same control structure.

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Unpacking nested arrays with list()

for()

for() will let you add new ones, the limit you pass will be evaluated each time, so count($your_array) can be dynamic. Example:

$original = array('one', 'two', 'three');
for($i = 0; $i < count($original); $i++) {
    echo $original[$i] . PHP_EOL;
    if($i === 2)
        $original[] = 'four (another one)';
};

Output:

one
two
three
four (another one)

while()

You can also define your own custom while() loop structure using a while(true){ do } methodology.

Disclaimer: Make sure if you're doing this that you define an upper limit on where your logic should stop. You're essentially taking over the responsibility of making sure that the loop stops somewhere here instead of giving PHP a limit like foreach() does (size of array) or for() where you pass a limit.

$original = array('one', 'two', 'three');
// Define some parameters for this example
$finished = false;
$i = 0;
$start = 1;
$limit = 5;

while(!$finished) {
    if(isset($original[$i])) {
        // Custom scenario where you'll add new values
        if($i > $start && $i <= $start + $limit) {
            // ($i-1) is purely for demonstration
            $original[] = 'New value' . ($i-1);
        }

        // Regular loop behavior... output and increment
        echo $original[$i++] . PHP_EOL;
    } else {
        // Stop the loop!
        $finished = true;
    }
}

See the differences here.

(PHP 4, PHP 5, PHP 7, PHP 8)

The foreach construct provides an easy way to iterate over arrays. foreach works only on arrays and objects, and will issue an error when you try to use it on a variable with a different data type or an uninitialized variable. There are two syntaxes:

foreach (iterable_expression as $value)
    statement
foreach (iterable_expression as $key => $value)
    statement

The first form traverses the iterable given by iterable_expression. On each iteration, the value of the current element is assigned to $value.

The second form will additionally assign the current element's key to the $key variable on each iteration.

Note that foreach does not modify the internal array pointer, which is used by functions such as current() and key().

It is possible to customize object iteration.

In order to be able to directly modify array elements within the loop precede $value with &. In that case the value will be assigned by reference.

$arr = array(1, 2, 3, 4); foreach ($arr as &$value) { $value = $value * 2; } // $arr is now array(2, 4, 6, 8) unset($value); // break the reference with the last element ?>

Warning

Reference of a $value and the last array element remain even after the foreach loop. It is recommended to destroy it by unset(). Otherwise you will experience the following behavior:

$arr = array(1, 2, 3, 4); foreach ($arr as &$value) { $value = $value * 2; } // $arr is now array(2, 4, 6, 8)

// without an unset($value), $value is still a reference to the last item: $arr[3]

foreach ($arr as $key => $value) {
    // $arr[3] will be updated with each value from $arr...
    echo "{$key} => {$value} ";
    print_r($arr);
}
// ...until ultimately the second-to-last value is copied onto the last value// output:
// 0 => 2 Array ( [0] => 2, [1] => 4, [2] => 6, [3] => 2 )
// 1 => 4 Array ( [0] => 2, [1] => 4, [2] => 6, [3] => 4 )
// 2 => 6 Array ( [0] => 2, [1] => 4, [2] => 6, [3] => 6 )
// 3 => 6 Array ( [0] => 2, [1] => 4, [2] => 6, [3] => 6 )?>

It is possible to iterate a constant array's value by reference:

foreach (array(1, 2, 3, 4) as &$value) { $value = $value * 2; } ?>

Note:
foreach does not support the ability to suppress error messages using @.

Some more examples to demonstrate usage:

/* foreach example 1: value only */$a = array(1, 2, 3, 17);

foreach (

$a as $v) {
    echo "Current value of \$a: $v.\n";
}/* foreach example 2: value (with its manual access notation printed for illustration) */$a = array(1, 2, 3, 17);$i = 0; /* for illustrative purposes only */foreach ($a as $v) {
    echo "\$a[$i] => $v.\n";
    $i++;
}/* foreach example 3: key and value */$a = array(
    "one" => 1,
    "two" => 2,
    "three" => 3,
    "seventeen" => 17
);foreach ($a as $k => $v) {
    echo "\$a[$k] => $v.\n";
}/* foreach example 4: multi-dimensional arrays */
$a = array();
$a[0][0] = "a";
$a[0][1] = "b";
$a[1][0] = "y";
$a[1][1] = "z";foreach ($a as $v1) {
    foreach ($v1 as $v2) {
        echo "$v2\n";
    }
}/* foreach example 5: dynamic arrays */foreach (array(1, 2, 3, 4, 5) as $v) {
    echo "$v\n";
}
?>

Unpacking nested arrays with list()

(PHP 5 >= 5.5.0, PHP 7, PHP 8)

It is possible to iterate over an array of arrays and unpack the nested array into loop variables by providing a list() as the value.

For example:

$array = [ [1, 2], [3, 4], ];

foreach (

$array as list($a, $b)) {
    // $a contains the first element of the nested array,
    // and $b contains the second element.
    echo "A: $a; B: $b\n";
}
?>

The above example will output:

You can provide fewer elements in the list() than there are in the nested array, in which case the leftover array values will be ignored:

$array = [ [1, 2], [3, 4], ];

foreach (

$array as list($a)) {
    // Note that there is no $b here.
    echo "$a\n";
}
?>

The above example will output:

A notice will be generated if there aren't enough array elements to fill the list():

$array = [ [1, 2], [3, 4], ];

foreach (

$array as list($a, $b, $c)) {
    echo "A: $a; B: $b; C: $c\n";
}
?>

The above example will output:

Notice: Undefined offset: 2 in example.php on line 7
A: 1; B: 2; C: 

Notice: Undefined offset: 2 in example.php on line 7
A: 3; B: 4; C:

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programming php Key => $value

Php foreach add to array with key

for()

while()

Unpacking nested arrays with list()

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