Detailed explanation of the differences between the three PHP string delimiters

This article mainly shares with you the detailed explanation of the differences between the three PHP string delimiters. I hope it can help you.

The difference between single quotes, double quotes, <<< is as follows:

Previous: Today I suddenly encountered <<

1. Single quotes: 'a string'
\' is the only escape code and cannot embed variables (the included variables are not parsed and are just output as they are).

2. Double quotes: ”a $better string\n”
Standard escape codes can be used normally, and variables can be embedded (the included variables will be parsed by PHP).

3. "Here-doc" syntax: PHP delimiter

1 $a=1;  
2 echo <<<EOT  
3 <script language="JavaScript" type="text/JavaScript">  
4 var a = $a;  
5 alert(a);  
6 </script>  
7 EOT;

　<<

Its functions can be summarized into three points:

1. The function of the PHP delimiter is to output everything inside it as it is, including line breaks and other formats;

　2. Any special characters in the PHP delimiter do not need to be escaped and are written as usual;

　3. The PHP variables in the PHP delimiter will be replaced with their values ​​normally (php parse nested variables).

Notes:

1. The character EOT after <<< is self-defined. Anything is acceptable, but the character at the end must be the same. , they appear in pairs.

　2. Start with <<

3. Embedded PHP variables should be enclosed in {} when necessary to tell the PHP parser that this is a PHP variable, such as {$name} to avoid ambiguity. {} is not needed in other cases. .
Note:

Based on the above, it can be seen that the execution efficiency of single quotes is higher than the latter two. Therefore, it should be considered appropriately during use.

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