


Detailed explanation of the difference between using commas and dots for echo in PHP
The editor below will share with you a detailed explanation of the difference between using commas and dots for echo in PHP. It has a good reference value and I hope it will be helpful to everyone. Let’s follow the editor and take a look.
The examples are as follows:
<?php //点和逗号的测试,涉及到字符串的强制转换 echo 1+5; echo "<br /><br />"; echo '1+5='."1+5"."<br />"; echo '1+5='."5+1","<br /><br />"; echo '1+5=',1,"<br />"; //用逗号,不需要空格 echo '1+5='. 1,"<br />"; //用连接符,需要空格,否则报错 echo '1+5=',100+200,"<br /><br />"; //用逗号,常用于输出多个变量,不影响输出 //省去了字符串拼接的步骤,理论上在 echo 的时候用“逗号”会快一点。 //换成用连接符,注意了,看以下测试: echo '注意了!<br />'; echo '1+5='. 100,"<br />"; //注意 .和100之间需要空格,否则报错 echo '1+5='. 200,"<br />"; echo '1+5='. 100+200,"<br />"; //此处结果开始异常了 echo '1+5='. 200+100,"<br />"; echo ('1+5='. 200)+100,"<br />"; //从与上面的结果相同可以看出,连接符的优先级高于运算符 echo "<br />"; //先来看看字符串的强制转换 echo (int)'abc1'; echo "<br />"; echo (int)'1abc'; echo "<br />"; echo (int)'22abc'; echo "<br /><br />"; //结果:将一个字符串强制转换成一个数字,PHP会去搜索这个字符串的开头, //如果开头是数字就转换,如果不是就直接返回0. //回到测试的问题 echo '结果分析:'; echo '1+5='. 100+200,"<br />"; /* 程序是这样执行的, * 先连接 '1+5='.100 结果是字符串 '1+5=100', * 然后执行运算,字符串要与数字进行运算会被系统强制转换,字符串'1+5=100'转换后的值就是1, * 最后1+200=201. */ /* 用逗号为什么没问题呢? 手册上说了:用逗号是multiple parameters .也就是说是多参数, 换句话说,逗号分隔开的就相当于是N个参数.也就是说把echo当个函数用, 这样的话,echo会对每个参数先进行计算,最后再进行分别输出,所以我们用逗号就不存在上面的问题了 */ ?>
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