In-depth understanding of the count function of PHP arrays

This article provides an in-depth analysis of the count function of PHP arrays. To give you a reference, I hope it will be helpful to everyone.

count()

PHP count() function is used to count the number of cells in an array or the number of attributes in an object, and returns an array The number of units or the number of attributes in the object.

Syntax:

int count(mixed var [, int mode]) If var is an ordinary variable that is not an array, it returns 1. If it does not exist, is not initialized, or An empty array returns 0.

Optional parameter mode is set to COUNT_RECURSIVE (or 1), count() will count the array recursively, which is especially useful for counting all cells of a multi-dimensional array, but count() does not recognize infinite recursion. The default value of mode is 0 .

Example:

<?php
echo count($x);      //输出：0
$a = 2;
echo count($a);      // 输出：1
$arr_age = array(18, 20, 25);
echo count($arr_age);    // 输出：3
?>

sizeof() is the alias of this function.

In practical applications, some loop operations are often performed based on the size of the array. It is recommended to write count() outside the loop:

<?php
$arr_age = array(18, 20, 25);
$count = count($arr_age);
for($i=1;$i<=$count;$i++){
  echo "第 $i 次循环";
}
?>

This way you don’t have to go through it every time Perform a count() calculation, although this is not required.

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