如果是单引号,PHP不解析其中的内容,直接当作一个字符串操作,如果是双引号,PHP会自动用变量的值替换掉变量名称,所以在处理字符串的时候最好使用单引号,这样速度快一些
如: $a = 5;
echo "$a"; //5
echo '$a'; //$a
双引号字符串最重要的一点是其中的变量名会被变量值替代
$var1 = "Chris Mao";
$var2 = &$var1; //引用传递$var1的值随着$var2的变化而变化
echo 'The value of $var2 is: ', $var2, "
";
//值是The value of $var2 is: Chris Mao
$var2 = 'my name is $var2';
echo 'The value of $var1 is: ', $var1, "
";
//值是The value of $var1 is: my name is $var2
$var2 = "my New name is $var1";
//在这个双引号里面就已经把$var1变量前面的值给替代了
echo 'The value of $var2 is: ', $var2, "
";
//值是The value of $var2 is: my New name is my name
is $var2
echo 'The value of $var1 is: ', $var1, "
";
//值是The value of $var2 is: my New name is my name
is $var2
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