PHP determines whether the value is in the array

In PHP, we can use the in_array() function to determine whether a given value exists in an array.

Function prototype: in_array($value, $array);

This function receives two parameters. $value represents the value to be found, and $array represents the array to be found.

If the $value value exists in the $array array, the in_array() function will return true; otherwise, it will return false.

For example:

//定义一个数组
$fruits = array('apple', 'banana', 'orange');

//判断 'apple' 是否在数组中
if(in_array('apple', $fruits)){
    echo "'apple' 在数组中";
}else{
    echo "'apple' 不在数组中";
}

Running the above code will output "'apple' in the array".

In addition to using the in_array() function, we can also use the array_search() function to determine whether a given value exists in the array.

Function prototype: array_search($value, $array);

This function also receives two parameters. $value represents the value to be found, and $array represents the array to be found.

If the $value value exists in the $array array, the array_search() function will return the key name of the value in the array; otherwise, it will return false.

For example:

//定义一个数组
$fruits = array('apple', 'banana', 'orange');

//判断 'banana' 是否在数组中
$key = array_search('banana', $fruits);
if($key !== false){
    echo "'banana' 在数组中，键名为：" . $key;
}else{
    echo "'banana' 不在数组中";
}

Running the above code will output "'banana' in the array, key name: 1".

It should be noted that the above two functions use weak type comparison (that is, using the == operator instead of the === operator) when determining whether the value is in the array. If you want to use strict type comparison, you can convert both $value and the elements in the array to the appropriate type before comparison.

For example:

//定义一个数组
$nums = array(1, 2, 3);

//判断 '2' 是否在数组中
if(in_array('2', $nums, true)){ //第三个参数指定为 true，表示使用严格类型比较
    echo "'2' 在数组中";
}else{
    echo "'2' 不在数组中";
}

Running the above code will output "'2' is not in the array".

In addition to the above two functions, there are many other array processing functions in PHP. Proficiency in these functions allows us to deal with array-related issues more conveniently.

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