从数组中删除所有不以某个字符串开头的元素

foreach($arr as $key => $value)
{
if(preg_match('/^foo-/', $key))
{
// You can access $value or create a new array based off these values
}
}

This is how I would do it, though I can't give you a more efficient advice before understanding what you want to do with the values you get.

$search = "foo-";
$search_length = strlen($search);
foreach ($array as $key => $value) {
if (substr($key, 0, $search_length) == $search) {
...use the $value...
}
}

Functional approach:

$array = array_filter($array, function($key) {
return strpos($key, 'foo-') === 0;
}, ARRAY_FILTER_USE_KEY);

Procedural approach:

$only_foo = array();
foreach ($array as $key => $value) {
if (strpos($key, 'foo-') === 0) {
$only_foo[$key] = $value;
}
}

Procedural approach using objects:

$i = new ArrayIterator($array);
$only_foo = array();
while ($i->valid()) {
if (strpos($i->key(), 'foo-') === 0) {
$only_foo[$i->key()] = $i->current();
}
$i->next();
}

$arr_main_array = array('foo-test' => 123, 'other-test' => 456, 'foo-result' => 789);


foreach($arr_main_array as $key => $value){
$exp_key = explode('-', $key);
if($exp_key[0] == 'foo'){
$arr_result[] = $value;
}
}


if(isset($arr_result)){
print_r($arr_result);
}

From PHP 5.3 you can use the preg_filter function: here

$unprefixed_keys = preg_filter('/^foo-(.*)/', '$1', array_keys( $arr ));


// Result:
// $unprefixed_keys === array('bcd','def','xyz')

Modification to erisco's Functional approach,

array_filter($signatureData[0]["foo-"], function($k) {
return strpos($k, 'foo-abc') === 0;
}, ARRAY_FILTER_USE_KEY);

this worked for me.

Simply I used array_filter function to achieve the solution as like follows

<?php


$input = array(
'abc' => 0,
'foo-bcd' => 1,
'foo-def' => 1,
'foo-xyz' => 0,
);


$filtered = array_filter($input, function ($key) {
return strpos($key, 'foo-') === 0;
}, ARRAY_FILTER_USE_KEY);


print_r($filtered);

Output

Array
(
[foo-bcd] => 1
[foo-def] => 1
[foo-xyz] => 0
)

For live check https://3v4l.org/lJCse

In addition to @Suresh Velusamy's answer above (which needs at least PHP 5.6.0) you can use the following if you are on a prior version of PHP:

<?php


$input = array(
'abc' => 0,
'foo-bcd' => 1,
'foo-def' => 1,
'foo-xyz' => 0,
);


$filtered = array_filter(array_keys($input), function($key) {
return strpos($key, 'foo-') === 0;
});


print_r($filtered);


/* Output:
Array
(
[1] => foo-bcd
[2] => foo-def
[3] => foo-xyz
)
// the numerical array keys are the position in the original array!
*/


// if you want your array newly numbered just add:
$filtered = array_values($filtered);


print_r($filtered);


/* Output:
Array
(
[0] => foo-bcd
[1] => foo-def
[2] => foo-xyz
)
*/

From PHP5.6, the array keys can be the sole subject of the filtration by using the ARRAY_FILTER_USE_KEY constant/flag.

From PHP7.4, arrow functions make custom functions more concise and allow values to be passed into the custom function's scope without use().

From PHP8, str_starts_with() can take the place of strpos(...) === 0

Code: (Demo)

$array = [
'abc' => 0,
'foo-bcd' => 1,
'foo-def' => 1,
'foo-xyz' => 0,
];


$prefix = 'foo';


var_export(
array_filter(
$array,
fn($key) => str_starts_with($key, $prefix),
ARRAY_FILTER_USE_KEY
)
);

Output:

array (
'foo-bcd' => 1,
'foo-def' => 1,
'foo-xyz' => 0,
)

You might pass a key-value single dimensional array and a specific prefix string 'foo-' to the function just made: filter_array_key_with_prefix

<?php


function filter_array_key_with_prefix($arr, $prefix) {
return array_filter($arr, function($k) use ($prefix) {
return strpos($k, $prefix) === 0;
}, ARRAY_FILTER_USE_KEY);
}


$arr = array(
'abc' => 0,
'foo-bcd' => 1,
'foo-def' => 1,
'foo-xyz' => 0,
// ...
);


$filtered = filter_array_key_with_prefix($arr, 'foo-');


var_dump($filtered);

Output:

array(3) {
["foo-bcd"]=>
int(1)
["foo-def"]=>
int(1)
["foo-xyz"]=>
int(0)
}