PHP 7 performance optimization tips: How to use the isset function to determine whether a variable has been declared

PHP 7 Performance Optimization Tips: How to use the isset function to determine whether a variable has been declared

Introduction:
In PHP development, we often need to determine whether a variable has been declared. This is particularly important in situations such as when using an undeclared variable that produces an error. In PHP 7, for performance optimization reasons, we should try to use the isset function to determine whether a variable has been declared, instead of directly using functions such as empty and is_null.

Why use isset:
In versions before PHP 7, we may be accustomed to using the empty or is_null function to determine whether a variable is empty or undeclared. However, the isset function has higher performance than these functions. In PHP 7, using the isset function can achieve better performance than the empty and is_null functions, and in some cases, can improve the execution efficiency of the script.

isset function usage:
isset() function is used to detect whether a variable has been declared and whether the variable value is null. Returns true if the variable is declared and the value is not null; otherwise, returns false.

The following is the basic syntax of the isset function:
bool isset ( mixed $var [, mixed $... ] )

Code example:
The following is a use isset function Sample code:

<?php
$var1 = 100;
$var2 = null;

// 使用isset函数判断变量是否被声明
if(isset($var1)){
    echo '$var1已被声明。';
} else {
    echo '$var1未被声明。';
}

if(isset($var2)){
    echo '$var2已被声明。';
} else {
    echo '$var2未被声明。';
}
?>

Run the above sample code, the output is as follows:

$var1已被声明。
$var2未被声明。

In the above code, we declare $var1 and assign it a value of 100, while $var2 is assigned a value of null. By using the isset function, we can easily determine whether a variable has been declared.

Performance test:
In PHP 7, the performance of isset function is even better. To verify this, we can conduct the following performance test.

<?php
// 创建一个未声明的变量
$start_time = microtime(true);

for($i = 0; $i < 1000000; $i++){
    isset($var);
}

$end_time = microtime(true);
echo "使用isset函数耗时：" . ($end_time - $start_time) . "秒
";

// 创建一个已声明的变量
$start_time = microtime(true);

$var = null;

for($i = 0; $i < 1000000; $i++){
    isset($var);
}

$end_time = microtime(true);
echo "使用isset函数耗时：" . ($end_time - $start_time) . "秒
";
?>

Run the above performance test code, the results are as follows:

使用isset函数耗时：0.074735164642334秒
使用isset函数耗时：0.06268310546875秒

It can be seen that using the isset function to judge declared variables has better performance, while on undeclared variables, The isset function also performs better.

Conclusion:
In PHP 7, in order to obtain better performance, we should try to use the isset function to determine whether the variable has been declared. By using the isset function, we can effectively avoid errors caused by using undeclared variables and achieve higher script execution efficiency. So, in PHP 7 development, let us use the isset function as the preferred method to determine whether a variable has been declared.

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