php echo print print_r三者区别分析
echo是PHP语句,print和print_r是函数,语句没有返回值,函数可以有返回值(即便没有用)
print() 只能打印出简单类型变量的值(如int,string)
print_r() 可以打印出复杂类型变量的值(如数组,对象)
echo 输出一个或者多个字符串
echo — 输出一个或者多个字符串
定义和用法
echo() 函数输出一个或多个字符串。
语法:echo(strings)参数 描述
strings 必需。一个或多个要发送到输出的字符串。
提示和注释
注释:echo() 实际上不是一个函数,因此您无需对其使用括号,不过,如果您希望向 echo() 传递一个或多个参数,那么使用括号会发生解析错误.
提示:echo() 函数比 print() 函数快一点点。
提示:echo() 函数可以使用简化语法,参见例子 5.
例子 1
- <?php
- $str = "Who's John Adams?";
- echo $str;
- echo "<br />";
- echo $str."<br />I don't know!";
- ?>
- //输出:
- //Who's John Adam?
- //Who's John Adam?
- //I don't know!
- //Descrīption
- void echo ( string arg1 [, string …] ) //返回值为空
- echo "你好"," 朋友";
print –输出一个字符串
print() 函数输出一个或多个字符串。
语法:print(strings)参数 描述
strings 必需,发送到输出的一个或多个字符串。
提示和注释
注释:print() 函数实际上不是函数,所以您不必对它使用括号.
注释:print() 函数稍慢于 echo().
描述:
int print ( string arg )//返回值为整形
print "你好朋友";
可以进行下面操作:
- $name=print "nihao n";
- $str = 'test print value is $name .';
- eval("$print="$str";");
- echo $print;
print_r — 打印关于变量的易于理解的信息。
bool print_r ( mixed expression [, bool return] ) //返回值是布尔型的,参数是mix类型的,可以是字符串,整形,数组,对象类print_r() 显示关于一个变量的易于理解的信息。如果给出的是 string、integer 或 float,将打印变量值本身。如果给出的是 array,将会按照一定格式显示键和元素。object 与数组类似。
print_r() 将把数组的指针移到最后边。
你可以
print_r(str);
print_r(int);
print_r(array);
print_r(obj);
也可以用var_dump var_export
php 中 print_r 函数输出的数组内容不排列,为了让它输出的好看些,如,数组有多层,分段列出,我们可以这样写:
- echo "<pre>";
- print_r xxxxx;
- echo "<pre>";
波比源码 » php echo print print_r三者区别分析
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