Table of Contents
The difference between equality (==) and congruent (===)
Size comparison (>, <, >=, <=)
Compare arrays and objects in small details
Home Backend Development PHP Tutorial PHP Comparison Operators

PHP Comparison Operators

Jul 18, 2025 am 04:57 AM
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PHP comparison operators need to pay attention to type conversion issues. 1. Use == to compare values only, and type conversion will be performed, such as 1=="1" is true; 2. Use === to determine whether the value and type are the same, such as 1==="1" is false; 3. Size comparison can be applied to numerical values and strings, such as "apple"

PHP Comparison Operators

Determining whether the two variables are equal or which one is larger is a very common operation in programming. PHP provides a variety of comparison operators to handle these requirements, but some details are easily confused, especially the problem of type conversion.

PHP Comparison Operators

The difference between equality (==) and congruent (===)

These two are the most commonly used and most error-prone ways to compare. == Compare values only, not types, and === Suppose that the values and types are consistent are considered "true".

For example:

PHP Comparison Operators
 1 == "1" // true, because PHP will automatically convert the string into the number 1 === "1" // false, one is an integer and the other is a string

It is recommended to use === and !== as much as possible during development, so as to avoid many unexpected results caused by type conversion.

Size comparison (>, <, >=, <=)

This type of operator is used to compare numerical sizes and can also be used to compare strings, but the logic behind it may not be as intuitive as you imagine.

PHP Comparison Operators

for example:

 "apple" < "banana" // true, compare character by character in alphabetical order 5 > "2 apples" // true, PHP will try to extract numbers from the beginning of the string for comparison

It should be noted that if one of the operands is a non-numeric string, the comparison results may be unexpected. Therefore, when processing user input or uncertain data types, it is best to do type conversion first.

Compare arrays and objects in small details

When comparing arrays, PHP is compared one by one according to key-value pairs:

 [1, 2] == [1, 2] // true
[1, 2] === [1, 2] // true, arrays are a special case in PHP, and only if the structure is exactly the same is true

Object comparison is a bit different. By default, == compares whether the object attribute values are the same, and === also ensures that it is the same instance. If you want to customize the comparison logic, you need to implement __toString() or use a special method.

Basically that's it. PHP's comparison rules seem simple, but if you are not careful in actual use, you will get stuck, especially in type conversion. Pay more attention to variable types and give priority to using congruent comparisons, which can reduce many bugs.

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