What function is used to obtain the length of a php array?

php has two functions to get the length of an array: 1. count(), the syntax "count($arr,$m)"; 2. sizeof(), the syntax "sizeof($arr,$m)" . The second parameter of these two functions is used to process multi-dimensional arrays and can be omitted; if the value is set to 1, the length of the multi-dimensional array can be calculated.

The operating environment of this tutorial: windows7 system, PHP8 version, DELL G3 computer

The method to obtain the array length in PHP is very simple, PHP is We provide two functions to calculate the length of an array, namely the count() and sizeof() functions.

1. count() function

count() function can count the number of all elements in the array, or the number of attributes in the object. Its syntax format is as follows :

count($array , $mode )

The parameter description is as follows:

• $array: is the array or object to be counted;
• $mode: is an optional parameter and can be omitted.
  • If the $mode parameter is omitted, or set to COUNT_NORMAL or 0, the count() function will not detect multidimensional arrays;
  • If $mode is set to COUNT_RECURSIVE or 1, the count() function Will recursively count the number of elements in the array, especially useful for counting the number of elements in multi-dimensional arrays.

Tip: If $array is neither an array nor an object, the count() function will return 1; if $array is equal to NULL, the count() function Return 0.

Example 1: Length of one-dimensional array

<?php 
header("content-type:text/html;charset=utf-8");
$arr=array(1,2,3,4,5,6,7,8,9);
var_dump($arr);
echo "数组长度为：".count($arr);
?>

Example 2: Length of two-dimensional array

<?php
header("Content-type:text/html;charset=utf-8");
$arr= array
("张三",
25,
    array("高数","PHP教程","英语"),
);
//输出语句
var_dump($arr);
echo "数组长度为：".count($arr,1);
?>

After reading the above output, are you confused? There are not only 5 elements in the array ("Zhang San", 25, "High Number", "PHP Tutorial", "English") , why does the array length displayed in the result not be 5, but 6?

In fact, this is because at this time, the count() function loops to count all elements in the two-dimensional array, and "array("高数","PHP tutorial","English")" will be regarded as an overall statistics Once, the elements in it ("Advanced Mathematics", "PHP Tutorial", "English") will be counted again, so the final result is 6.

2. sizeof() function

sizeof() function is an alias of count() function, that is, the function and usage of sizeof() function are the same as count () function is exactly the same.

Example: Use the sizeof() function to calculate the array length

<?php
header("Content-type:text/html;charset=utf-8");
$arr = [&#39;php中文网&#39;,&#39;PHP教程&#39;,&#39;https://www.php.cn/&#39;,&#39;sizeof()函数&#39;,&#39;数组长度&#39;];
echo &#39;$arr 的长度为：&#39;.sizeof($arr).&#39;<br>&#39;;
$arr2 = [&#39;php中文网&#39;,&#39;PHP教程&#39;,[&#39;https://www.php.cn/&#39;,&#39;sizeof()函数&#39;,&#39;数组长度&#39;]];
echo &#39;$arr2 的长度为：&#39;.sizeof($arr2).&#39;<br>&#39;;
echo &#39;参数 $mode = 1 时，$arr2 的长度为：&#39;.sizeof($arr2, 1).&#39;<br>&#39;;
?>

Recommended learning: "PHP Video Tutorial"

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