Introduction to various operators in php and examples

An

operator is something that takes one or more given values ​​(an expression, in programming jargon) and produces another value (thus the entire structure becomes an expression).

1. Arithmetic operators

Operator Name Result
$a + $b Addition Sum of $a and $b
$a - $b Subtraction The difference between $a and $b
$a * $b Multiplication The product of $a and $b
$a / $b Division The quotient of $a divided by $b
$a % $b Modulo The remainder of dividing $a by $b

2. Increment/Decrease Operator
Operator Name Result
++$a Before Add the value of $a plus one, and then perform the operation
$a++ Then add the value of $a first, perform the operation first, then add one
--$a Subtract the value of $a before subtraction by one, and then perform the operation
$a-- The value of $a is operated first, then decremented by one
Example:

<?php 
  echo  $a=5+”5th”;    //输出：10 
  echo  10%3;          //输出：1 
  echo  10+ $a++;      //输出：20 
  echo   5- --$a;        //输出：-5 
?>

3. Comparison operator
Operator Name Result
$a == $b is equal to TRUE if $a is equal to $b
$a === $b is congruent TRUE if $a is equal to $b and they are of the same type
$a != $b No etc. TRUE if $a is not equal to $b
$a a8093152e673feb7aba1828c43532094 $b is not equal TRUE if $a is not equal to $b
$a !== $b is not congruent TRUE if $a Not equal to $b, or they are of different types
$a 57fda13365877b4c578b2cdbbc0adb3d $b is greater than TRUE if $a is strictly $b
$a b25c5a3e7436edc83de0e458d4b26e56= $b Greater than or equal to TRUE if $a is greater than or equal to $b
Another conditional operator is " ? : " (or ternary) operator.
Example:

<?php 
     var_dump(0=="a");  //输出：bool(true)       
    var_dump(0=="00");      //输出：bool(true) 
    var_dump(0==="00");    //输出：bool(false) 
    var_dump(0<>"abc");   //输出：bool(false) 
    var_dump(0!=="01");  //输出：bool(true)  
    $a=10; 
    $b=20; 
    $str=$a>$b? "true":"false";  
    echo $str;    //输出：false  
?>

4. 逻辑运算符 
  运算符      名称      结果 
  $a and $b    逻辑与    TRUE，如果 $a 与 $b 都为 TRUE。 
  $a or $b    逻辑或    TRUE，如果 $a 或 $b 任一为TRUE。 
  $a xor $b    异或        TRUE，如果 $a 和 $b 不同时 
  ! $a              逻辑非  TRUE，如果 $a 不为 TRUE。 
  $a && $b      逻辑与  TRUE，如果 $a 与 $b 都为TRUE。 
  $a || $b        逻辑或  TRUE，如果 $a 或 $b 任一为TRUE。 
  其中and与&& 、or与||是同一逻辑运算符的两种写法。  
  逻辑与和逻辑或 都是短路运算符。

在遇到下列逻辑表达式时，PHP解释程序将不会计算右边的表达式： 

  <?php 
      $a=10; 
      if(false && (++$a)); 
      echo $a;      //输出：10 
      $b=10; 
      if(true or (++$b)); 
      echo $b;      //输出：10 
  ?>

5. 位运算符 
  位运算符允许对整型数中指定的位进行置位。如果左右参数都是字符串，则位运算符将操作字符的 ASCII 值。 
  表达式     名称      结果 
  $a & $b   按位与     将把 $a 和 $b 中都为 1 的位设为 1。 
  $a | $b     按位或    将把 $a 或者 $b 中为 1 的位设为 1。 
  $a ^ $b   按位异或  将把 $a 和 $b 中不同的位设为 1。 
  ~ $a       按位非    将 $a 中为 0 的位设为 1，反之亦然。 
  $a 4199223a77a3e66d1c0cfe54d715f43c> $b   右移      将 $a 中的位向右移动 $b 次（每一次                           移动都表示“除以 2”）。 

 其他运算符 
1. 字符串运算符 
有两个字符串运算符。第一个是连接运算符（“.”），它返回其左右参数连接后的字符串。第二个是连接赋值运算符（“.=”），它将右边参数附加到左边的参数后。 
错误抑制操作符 
在最常见的数据库连接与文件创建操作或出现除0等异常时，可以用@符号来抑制函数错误信息输出到浏览器端 $a=@(5/0) 
外部命令执行 
 使用``来运行外部系统命令，注意不是单引号，是ESC下面那个按键        

<?php 
  $out=`dir c:`; 
  print_r($out); 
?>
//不建议使用

实例： 

<?php 
  $a="hello"; 
  $a.=" world! ";  //等同于：$a=$a." world!"; 
  echo $a;  //输出：hello world!   
  $m = 3; 
  $m += 5;  //等同于：$m=$m+5; 
  echo $m;   //输出：8 
  $c = ($b = 4) + 5;  
  echo $c;  //输出：9   
?>

2. 运算符优先级  
下表从低到高列出了运算符的优先级。  
  结合方向    运算符 
  左      , 
  左      or 
  左      xor 
  左      and 
  右      print 
  右      = += -= *= /= .= %= &= |= ^=                      ~=   341666e55d71dd76c0b6e313fcc8374e>=  
  左      ? : 
  左      || 
  左      && 
结合方向        运算符 
  左      | 
  左      ^ 
  左      & 
  无      == != === !== 
  无      6e256fa4b1026ecd9077150abca744f9 >=  
  左      4dc0da33faa5301e003c483fcf957627> 
  左      +  -  . 
  左      *  /   % 
  右      ! ~ ++ -- (int) (float) (string) (array) (object) @ 
  右      [ 
  无      new

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