条件语句中的顺序

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可能重复: php处于错误状态的地方

Possible Duplicate: php false place in condition

我注意到很多PHP代码使用条件语句，例如CONST == VARIABLE.我长大后总是总是以相反的方式表达语法.有这种结构的原因吗?

I have noticed that a lot of PHP code uses conditional statements like CONST == VARIABLE. I grew up with the syntax always articulated in reverse. Is there a reason for this structure?

示例:

// this is the way I see it most typically represented in PHP if ( false == $foobar ) { // do this } // this is the way I normally do it if ( $foobar == false ) { // do this }

推荐答案

这是为了防止==和=之间的常见拼写错误，即所谓的yoda条件.请考虑以下内容:

This is to prevent a common typo between == and =, known as a yoda condition. Consider the following:

if( false = $foobar) {

这将导致错误，并捕获可能被视为错误的错误，因为您无法为false分配任何内容.相反:

This would result in an error, catching what would be considered a bug, since you cannot assign anything to false. On the contrary:

if( $foobar = false) {

这是有效的语法，很容易犯错.

This is valid syntax, and is quite an easy mistake to make.

但是，我通常更喜欢if( $foobar == false)语法，因为单元测试应该能够捕获这些程序错误.

However, I typically prefer the if( $foobar == false) syntax, as unit tests should be able to catch these programmatic mistakes.