Home > Article > Backend Development > A brief analysis of the difference between == and === in php
In PHP, sometimes we need to compare whether two variables are equal. In order to achieve this function, we can use the equal operator "==" or the congruent operator "===". Although both operators can perform equality comparisons, there are some differences between them.
In this article, we will introduce the specific functions of "==" and "===" respectively, and discuss their differences and usage scenarios in detail.
1. "==" operator
The "==" operator is the equal operator in PHP, which is used to compare whether the values of two variables are equal. For example:
$x = 4;
$y = "4";
if ($x == $y) {
echo "变量x和y的值相等";
}
In the above example, although $x and $y have different types, their values are equal. Therefore, using the "==" operator determines that the result is true and outputs "the values of variables x and y are equal."
However, it should be noted that the "==" operator only compares values, regardless of the data type of the variable. Therefore, it is possible that some comparison results may not meet expectations.
For example, in the following example:
$x = 0;
$y = "abc";
if ($x == $y) {
echo "变量x和y的值相等";
}
Although the data types and values of $x and $y are different, the "==" operator is used for comparison, and the output result is " The values of variables x and y are equal".
2. "===" operator
The "===" operator is the congruence operator in PHP, which is used to compare two variables. Whether both value and data type are equal. For example:
$x = 4;
$y = "4";
if ($x === $y) {
echo "变量x和y的值和数据类型都相等";
}
In the above example, the values of $x and $y are equal, but the types are different. Therefore, using the "===" operator for comparison will result in false and nothing will be output.
3. The difference between “==” and “===”
“==” The operator only compares the values of variables for equality, regardless of whether the variable types are equal. The "===" operator compares whether the values and types of variables are equal.
When the two variable types and values are equal, the results of using the "==" operator and the "===" operator are both true . But when the types of variables are different, the results of using the "==" operator and the "===" operator may be different.
For example, in the following example:
$x = 1;
$y = "1";
if ($x == $y) {
echo "值相等";
}
if ($x === $y) {
echo "值和类型都相等";
}
Use the "==" operator for comparison, the output result is "equal values"; use the "===" operator for comparison, no Output anything.
4. Usage scenarios
In most cases, it is recommended Use the "===" operator for variable comparison. This ensures the accuracy of the comparison results and avoids some unexpected comparison results.
When some type conversion is required, the "==" operator can be used. For example, when you need to convert a string to an integer, you can use the "==" operator, as shown below:
$x = "4";
if ($x == 4) {
echo "转换成功";
}
In some other scenarios , when performing array comparison, you can use the "==" operator.
$x = array("a" => "apple", "b" => "banana");
$y = array("a" => "apple", "b" => "banana");
if ($x == $y) {
echo "数组相等";
}
In short, the choice of operator needs to be decided according to the actual situation, and in most cases, it is recommended to use the "===" operator for variable comparison to ensure the correctness of the comparison results.
The above is the detailed content of A brief analysis of the difference between == and === in php. For more information, please follow other related articles on the PHP Chinese website!