PHP函数echo()的定义和用法解析

在使用定义和用法

PHP函数echo()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：PHP函数echo()可以使用简化语法。参见以下示例。

<ol class="dp-xml"><li class="alt"><span><span class="tag"><span class="tag-name">html</span><span class="tag">></span><span> </span><span class="tag"><span class="tag-name">body</span><span class="tag">></span><span> </span></span><li class="alt"><span><span></span><span class="tag"></span><span class="tag-name">php</span><span> $</span><span class="attribute">color</span><span> = </span><span class="attribute-value">"red"</span><span>; </span><span class="tag">?></span></span></li></span><li class="alt"><span><span class="tag"><span class="tag"></span><span> </span><span class="tag"><span class="tag-name">p</span><span class="tag">></span><span>Roses are </span></span></span><li class="alt"><span><span class="tag"><span></span><span class="tag"></span><span>=$color</span><span class="tag">?></span></span></span></li></span></li>
<li class="alt"><span><span class="tag"><span class="tag"><span class="tag"><span class="tag"><span class="tag-name">p</span><span class="tag">></span></span></span></span></span><li class="alt"><span><span class="tag"><span class="tag"><span class="tag"><span class="tag"></span><span> <span class="tag"><span class="tag-name">body</span><span class="tag">></span><span> </span></span></span></span></span></span><li class="alt"><span><span class="tag"><span class="tag"><span class="tag"><span class="tag"><span><span class="tag"><span class="tag-name">html</span><span class="tag">></span><span> </span></span></span></span></span></span></span></span></li></span></li></span></li></span></li></ol>

 1.echo 输出标量

<ol class="dp-xml">
<li class="alt"><span><span class="tag"></span><span class="tag-name">php</span><span> </span></span></li>
<li><span>  echo 123adb; //输出正确  </span></li>
<li class="alt"><span>  echo 123abd; //正确  </span></li>
<li><span>  echo "123adb"; //正确  </span></li>
<li class="alt">
<span class="tag">?></span><span> </span>
</li>
</ol>

2、PHP函数echo()输出变量，常量

<ol class="dp-xml">
<li class="alt"><span><span class="tag"></span><span class="tag-name">php</span><span> </span></span></li>
<li>
<span>$</span><span class="attribute">a</span><span>=</span><span class="attribute-value">"123456"</span><span>;  </span>
</li>
<li class="alt"><span>echo $a;  //正确  </span></li>
<li>
<span>echo "</span><span class="tag"><span class="tag-name">br</span><span class="tag">></span><span>";  </span><li class="alt"><span>echo "$a"; //正确  </span></li>
<li>
<span>echo "</span><span class="tag"><span class="tag-name">br</span><span class="tag">></span><span>";  </span><li class="alt"><span>echo $a;//不正确  </span></li>
<li>
<span>echo "</span><span class="tag"><span class="tag-name">br</span><span class="tag">></span><span>";  </span><li class="alt"><span>echo abcdef;  //也能正确的显示，但是强烈不建议这么做，<br>因为有很多特殊符号这么做不能正确的显示。  </span></li>
<li>
<span>echo "</span><span class="tag"><span class="tag-name">br</span><span class="tag">></span><span>";  </span><li class="alt">
<span>//echo </span><span class="tag"><span class="tag-name">abd</span><span class="tag">></span><span>;  //比如说这样，带了尖括的，就不能用，<br>你可以去了前面的注释试试会不会报错。  </span><li>
<span>echo "</span><span class="tag"><span class="tag-name">br</span><span class="tag">></span><span>";  </span><li class="alt">
<span>$</span><span class="attribute">b</span><span>=</span><span class="attribute-value">10</span><span>;  </span>
</li>
<li><span>echo $b+10; //显示 20  </span></li>
<li class="alt">
<span>echo "</span><span class="tag"><span class="tag-name">br</span><span class="tag">></span><span>";  </span><li><span>echo "$b+10";  </span></li>
<li class="alt">
<span>echo "</span><span class="tag"><span class="tag-name">br</span><span class="tag">></span><span>";  </span><li><span>echo "结果是："."$b"; //这两种写法的效果是一样的。  </span></li>
<li class="alt">
<span>echo "</span><span class="tag"><span class="tag-name">br</span><span class="tag">></span><span>";  </span><li><span>echo "结果是：$b";  //这两种写法的效果是一样的。  </span></li>
<li class="alt">
<span class="tag">?></span><span> </span>
</li></span>
</li></span>
</li></span>
</li></span>
</li></span>
</li></span>
</li></span>
</li></span>
</li></span>
</li>
</ol>

echo ""和PHP函数echo()是有区别的，加双引号时会对变量与特定的符号进行转义，加单引号时不会进行转义，会将单引号内的符号直接的输出，所以说用单引号比用双引号时更快一点。能不用双引号时就不要用了吧。