# Php comparison operator

Source: Internet
Author: User
Tags php tutorial

Php Tutorial comparison operator
A comparison operation compares two values to reflect the relationship between two numbers.
Example name result
\$ A = \$ B is equal to TRUE if \$ a is equal to \$ B.
\$ A ===\$ B all equal to TRUE, if \$ a is equal to \$ B, and their types are the same.
\$! = \$ B is not equal to TRUE, if \$ a is not equal to \$ B.
\$ A <> \$ B is not equal to TRUE, if \$ a is not equal to \$ B.
\$! = \$ B is not equal to TRUE. If \$ a is not equal to \$ B, or they have different types.
\$ A <\$ B small and TRUE, if \$ a is strictly less than \$ B.
\$ A> \$ B is greater than TRUE if \$ a is strict with \$ B.
\$ A <= \$ B is less than or equal to TRUE, if \$ a is less than or equal to \$ B.
\$ A >=\$ B is greater than or equal to TRUE if \$ a is greater than or equal to \$ B.

<? Php
\$ A = 10;
\$ B = 10;
Echo \$ a = \$ B; // \$ a = \$ B? 10 = 10 returns 1 True
Echo "<br/> ";

Echo \$ a ===\$ B; // \$ a ===\$ B? 10 = 10 returns 1 True
Echo "<br/> ";

\$ B = "10 ";
Echo \$ a ===\$ B; // \$ a ===\$ B? 10 = "10" return null false to compare two data types, not only the data value but also the data type;
Echo "<br/> ";

\$ A = 10;
\$ B = 20;
Echo \$! = \$ B; // \$ a is not equal to \$ B 10! = 20 returns 1 True
Echo "<br/> ";

Echo \$ A <> \$ B; // \$ a is not equal to \$ B 100 <> 20. Return 1 True.
Echo "<br/> ";

Echo \$! ==\$ B; // \$ a is not equal to \$ B, or they have different types. 10! = 20 returns 1 True
Echo "<br/> ";

\$ C = "10 ";
Echo \$! ==\$ C; // non-full equality \$ a is not equal to \$ B, or they have different types. 10! = "10" return null false
Echo "<br/> ";

Echo \$ A <\$ B; // \$ a must be less than \$ B 10 <20 returns 1 True
Echo "<br/> ";

Echo \$ A> \$ B; // \$ a must be less than \$ B 10> 20. Return null false.
Echo "<br/> ";

Echo \$ A <= \$ B; // \$ a less than or equal to \$ B 10 <= 20 returns 1 True
Echo "<br/> ";

Echo \$ A >=\$ B; // \$ a is greater than or equal to \$ B 10 >=20 returns null false
Echo "<br/> ";
?>

Comparison of multiple types of operations 1 type of operations 1 type of results
Null or string converts NULL to "" for comparison of numbers or words
Bool or null any other type is converted to bool, FALSE <TRUE
Object built-in classes can define their own comparisons. Different classes cannot be compared. The same classes and arrays are used to compare attributes (in PHP 4). PHP 5 has its own instructions.
String, resource, or number string, resource, or number converts a string and a resource to a number.
Array has a small array of fewer members. If the key in Operation Number 1 does not exist in Operation Number 2, the array cannot be compared; otherwise, the values are compared one by one (see the following example)
Array any other type of array is always larger
Any other object type of the object is always larger.

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