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HomeBackend DevelopmentPHP TutorialSummary of common judgment conditions in PHP

Types of commonly used judgment conditions

  • Variables such as: $var

  • isset()

  • empty()

  • Comparison operators such as: >

  • ##Logical operations Symbols such as:! && || or and

  • Specific type judgment, for example: is_null()/is_array()/is_int(), etc.

Variable

  • No matter what type the variable is, it will be converted to bool type

  • Empty strings and empty arrays are false

  • The value 0 and the string "0" are both false

  • The NULL type is false

NULL类型有三种情况:
1、定义并赋值为null
2、定义不赋值
3、不定义(不存在的)
isset()

  • is mainly used to determine the NULL type. For other types, no matter what the value is, it is true

  • and is_null() are a pair of opposite functions.

empty()

  • and variables are a pair that have exactly the opposite effect

  • The range of judgment Larger than isset()

  • Empty strings and empty arrays are both true

  • The value 0 and the string "0" are both true

  • NULL types are all true

Types of commonly used judgment conditions

  • Variable example: $var

  • isset()

  • empty()

  • Comparison operators such as: >
  • Logical operators such as: ! && || or and

  • Specific type judgment, for example: is_null()/is_array()/is_int(), etc.

Variable

  • No matter what type the variable is, it will be converted to bool type

  • Empty strings and empty arrays are false

  • The value 0 and the string "0" are both false

  • The NULL type is false

NULL类型有三种情况:
1、定义并赋值为null
2、定义不赋值
3、不定义(不存在的)
isset()

  • is mainly used to determine the NULL type. For other types, no matter what the value is, it is true

  • and is_null() are a pair of opposite functions.

empty()

  • and variables are a pair that have exactly the opposite effect

  • The range of judgment Larger than isset()

  • Empty strings and empty arrays are both true

  • The value 0 and the string "0" are both true

  • NULL types are all true

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