php insert value into array of arrays using foreach

Question

I have a pretty basic question but I am stuck. I am pretty new to php and I have an array like this:

$array = array(
    'one' => 1,
    'two' => array('key1' => 'val1','key2' => 'val2'),
    'three' => array('key1' => 'val1','key2' => 'val2'),
    'four' => array('key1' => 'val1','key2' => 'val2')
);

and for each of the arrays in the array (that is, 'two, 'three', and 'four'), I want to insert 'key3' => 'val3' into those arrays.

I tried this:

foreach($array as $item) {
    if (gettype($item) == "array") {
        $item['key3'] = 'val3';
    }
}

But it doesn't work, and I'm not sure why. Using various print_r's all over the place, it seems to insert 'key3' => 'val3' into $item if I print it out in the loop, but the original array seems unchanged. I also tried a regular for loop but that didn't work either.

curious why you didn't just do foreach ($array as $item_key => $item) { $array[$item_key]['key3'] = 'val3'; } — solomon
– solomon, Commented Apr 2, 2015 at 2:49

kapa · Accepted Answer · 2013-05-14 09:36:36Z

24

foreach works with a copy of $item, so you cannot modify your original array inside the foreach. One way to work around this is to use the & operator.

foreach($array as &$item) {
    if (is_array($item)) {
        $item['key3'] = 'val3';
    }
}

Another, more elegant way would be to use array_walk():

array_walk($array, function (&$v, $k) { 
    if (is_array($v)) {
        $v['key3'] = 'val3';
    }
});

This example will work from PHP 5.3, where Closures were introduced.

edited May 14, 2013 at 9:36

answered May 10, 2013 at 22:34

kapa

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6 Comments

moskito-x Over a year ago

$item is only generated for the loop . You mean &$array['key3'] = 'val3'; !

kapa Over a year ago

@moskito-x I certainly mean what I wrote. That's the point of it. Check the foreach manual page I linked.

moskito-x Over a year ago

To change $item is useless. Will be always overwritten by the next loop.

moskito-x Over a year ago

But As foreach relies on the internal array pointer changing it within the loop may lead to unexpected behavior. therefore you have to unset the reference . unset($item); // break the reference with the last element. structures.foreach

Benjamin Thvedt Over a year ago

Thanks for the great answer. The first solution worked fine but the second solution didn't seem to work, it's obvious I need to get a little better at php. Can I just stick that & symbol anywhere? Wow that would change things. Also, thanks for the tip on using unset($item), not knowing that would have eventually sunk me somewhere down the line for sure!

|

hek2mgl · Accepted Answer · 2013-05-10 22:33:59Z

0

PHP has a function to check whether a variable is an array or not: is_array(). Use this:

if (is_array($item)) { ...

answered May 10, 2013 at 22:33

hek2mgl

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Comments

Hamad · Accepted Answer · 2016-01-28 11:28:20Z

0

while looping with foreach use key like :

foreach($array as $key => $item){

    $array[$key]['newElement'] = "newValue";

}

edited Jan 28, 2016 at 11:28

Hamad

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answered Jan 28, 2016 at 11:10

Asad

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1 Comment

Mark Carpenter Jr Over a year ago

While not the answer to the question, this helped me better understand the relationship between the $key word and the $item.

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