The symbols in PHP

Double quotes are used to represent strings, except that the $ variable inside the double quotes is interpreted, for example:

12345

<?php    $n=123;    $s1="n=$n";//输出:n=123    $s2=‘n=$n‘;//输出:n=$n?>

Parentheses are required as function calls, or special syntactic constructs (if and for, etc.), which are similar to the C language and have nothing special, such as:

12345

<?php    $n=1;    if($n>=10) echo‘两位数‘;    else echo‘一位数‘;?>

The brackets are used in arrays, for example:

1234	<?php    $a=array(1,2,3);    echo$a[1];//输出2?>

Curly braces are used inside a string to represent the entire variable, for example:

123456

<?php    $a=123;    $aa=456;    echo"$aa";//输出456    echo"{$a}a";//输出123a?>

The symbols in PHP