How to count how many duplicate keys are in array?

Is is to possible to get how many 'a' are in a开发者_运维技巧rray?

$array = array( 'a', 'a', 'a', 'a', 'b', 'b', 'c' );

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array_count_values is what you need

<?php
$array = array( 'a', 'a', 'a', 'a', 'b', 'b', 'c' );
print_r(array_count_values($array));
?>

The above example will output:

Array
(
    [a] => 4
    [b] => 2
    [c] => 1
)

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Since you're just looking for a values, you could also use array_keys:

$array = array( 'a', 'a', 'a', 'a', 'b', 'b', 'c' );
$count = count(array_keys($array, 'a', true));
echo "Found $count letter a's.";

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Haim is correct. However I have had some speed issues with array_count_values before. So if you already know what value you are checking for, and don't need the others. A loop and counter can be faster. I'd benchmark.

EDIT

That is, unless the array is smaller than 1000-10,000 items. Then it is probably too small to matter.