takes a value as its first parameter and an array as its second and returns
true if the value is in the array.
With those functions out of the way, we can focus on the more interesting
functions, two of which are array_keys() and array_values(). They
both take an array as their only parameter and return a new array made up of
the keys in the array or the values of the array, respectively. Using the
array_values() function is an easy way to create a new array of the
same data, just without the keys. This is often used if you have numbered
your array keys, deleted several elements, and want to reorder the array.
The array_keys() function creates a new array where the values are the
keys from the old array, like this:
Click here to view code image
<?php
$myarr = array("foo" => "red", "bar" => "blue", "baz" => "green");
$mykeys = array_keys($myarr);
foreach($mykeys as $key => $value) {
echo "$key = $value\n";
}
?>
This prints “0 = foo”, “1 = bar”, and “2 = baz”.
Several functions are used specifically for array sorting, but only two get
much use: asort() and ksort(). asort() sorts an array by its values,
and ksort() sorts the array by its keys. Given the array $myarr from the
previous example, sorting by values would produce an array with elements in
the order bar/blue, baz/green, and foo/red. Sorting by key would
give the elements in the order bar/blue, baz/green, and foo/red. As
with the shuffle() function, both asort() and ksort() do their work
in place, meaning they return no value but directly alter the parameter you
pass in. For interest’s sake, you can also use arsort() and krsort() for
reverse value sorting and reverse key sorting, respectively.
This code example reverse sorts the array by value and then prints it, as
before:
Click here to view code image
<?php
$myarr = array("foo" => "red", "bar" => "blue", "baz" => "green");
arsort($myarr);
foreach($myarr as $key => $value) {
echo "$key = $value\n";
}
?>