编写php程序实现9*9乘法表的输出

可以使用双重循环来实现九九乘法表的输出，以下是PHP代码示例：

<?php
for ($i = 1; $i <= 9; $i++) {
    for ($j = 1; $j <= $i; $j++) {
        echo "$j * $i = " . ($j * $i) . "\t";
    }
    echo "\n";
}
?>

这段代码中，外层循环控制行数，内层循环控制列数，每次循环输出一个乘法表达式，并且使用制表符`\t`和换行符`\n`来控制格式。运行此代码，即可输出如下所示的九九乘法表：

1 * 1 = 1	
1 * 2 = 2	2 * 2 = 4	
1 * 3 = 3	2 * 3 = 6	3 * 3 = 9	
1 * 4 = 4	2 * 4 = 8	3 * 4 = 12	4 * 4 = 16	
1 * 5 = 5	2 * 5 = 10	3 * 5 = 15	4 * 5 = 20	5 * 5 = 25	
1 * 6 = 6	2 * 6 = 12	3 * 6 = 18	4 * 6 = 24	5 * 6 = 30	6 * 6 = 36	
1 * 7 = 7	2 * 7 = 14	3 * 7 = 21	4 * 7 = 28	5 * 7 = 35	6 * 7 = 42	7 * 7 = 49	
1 * 8 = 8	2 * 8 = 16	3 * 8 = 24	4 * 8 = 32	5 * 8 = 40	6 * 8 = 48	7 * 8 = 56	8 * 8 = 64	
1 * 9 = 9	2 * 9 = 18	3 * 9 = 27	4 * 9 = 36	5 * 9 = 45	6 * 9 = 54	7 * 9 = 63	8 * 9 = 72	9 * 9 = 81