How to determine if an array is empty in php

青灯夜游
Release: 2023-03-08 10:22:01
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Judgment method: 1. Use the isset() function to determine whether the elements in the array have been defined. If not, it will be an empty array; 2. Use the empty() function to check whether the array variable is empty. If it is empty, then It is an empty array; 3. Use "array variable == null" to determine whether the array variable is "empty". If it is empty, it is an empty array.

How to determine if an array is empty in php

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

PHP Determine whether it is 5 methods of empty array

1. isset function: determine whether the variable has been initialized

Explanation: It does not It will not determine whether the variable is empty, and can be used to determine whether the elements in the array have been defined

Note: When using isset to determine whether the array elements have been initialized, its efficiency is about 4 times higher than array_key_exists


        
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2. empty function: detect whether the variable is "empty"

Description: Any uninitialized variable, value is 0 or false or empty string "" Or null variables, empty arrays, and objects without any attributes will be judged as empty==true

Note 1: Uninitialized variables can also be detected as "empty" by empty

Note 2: empty can only detect variables, but not statements


        
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3. var == null Function: Determine whether the variable is "empty"

Description: Value Variables and empty arrays that are 0 or false or empty string "" or null will be judged as null

Note: The significant difference from empty is that var == null will report an error when the variable is not initialized.


        
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4. is_null function: detect whether the variable is "null"

Note: When the variable is assigned a value of "null", the detection result is true

Note 1: null is not case-sensitive: $a = null; $a = NULL makes no difference

Note 2: The detection result is true only when the value of the variable is "null". 0, empty string, false, and empty array are all detected as false

Note 3: When the variable is not initialized, The program will report an error


        
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5. var === null function: detect whether the variable is "null", and the type of the variable must also be "null"

Note: When a variable is assigned a value of "null" and the type of the variable is also "null", the detection result is true

Note 1: When it is judged to be "null", all Equal to the same effect as is_null

Note 2: When the variable is not initialized, the program will report an error

Summary:

In PHP, "NULL" and "empty" are 2 a concept.

isset is mainly used to determine whether a variable has been initialized.

empty can set variables with values of "false", "empty", "0", "NULL" and "uninitialized". Judged as TRUE

is_null Only variables whose value is "NULL" are judged as TRUE

var == null Judged as "false", "empty", "0", "NULL" All variables are judged to be TRUE

var === null. Only variables with a value of "NULL" are judged to be TRUE

. Note: When judging whether a variable is really "NULL", most of the Use is_null to avoid interference with values such as "false" and "0".

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