Summary of steps to use commas and periods for echo in PHP

This time I will bring you a summary of the steps for using commas and dots in echo in php. What are the precautions for using commas and dots in echo in php? The following is a practical case. Get up and take a look.

The example is as follows:

";
echo '1+5='."1+5"."
";
echo '1+5='."5+1","

";	
echo '1+5=',1,"
";			//用逗号，不需要空格
echo '1+5='. 1,"
";		//用连接符，需要空格，否则报错
echo '1+5=',100+200,"

"; //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！
';		
echo '1+5='. 100,"
";		//注意 .和100之间需要空格，否则报错
echo '1+5='. 200,"
";				
echo '1+5='. 100+200,"
";	//此处结果开始异常了
echo '1+5='. 200+100,"
";
echo ('1+5='. 200)+100,"
"; 	//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 "
";		
//先来看看字符串的强制转换
echo (int)'abc1';	echo "
";	
echo (int)'1abc';	echo "
";
echo (int)'22abc';	echo "

";
//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,"
";
/* 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
 */
?>

The result is as follows:

Detailed explanation of the steps to implement the mysql connection pool effect in php

PHP operation WeChat recording temporary transfer to permanent storage steps Detailed explanation

The above is the detailed content of Summary of steps to use commas and periods for echo in PHP. For more information, please follow other related articles on the PHP Chinese website!