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Home > Backend Development > PHP Tutorial > ，字符串，运算符，整型相加减。怎么写式子？

，字符串，运算符，整型相加减。怎么写式子？

WBOY
Release： 2016-06-23 13:15:38
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输出的$sum是一个式子
我希望它直接输出一个结果。
应该怎么办？


回复讨论(解决方案)

$a = '3';$b = '4';$c = '+';$sum = $a.$c.$b;echo $sum, PHP_EOL;//可以这样echo eval("return $sum;"), PHP_EOL;//也可以这样$f = create_function('', "return $sum;");echo $f();
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$a = '3';$b = '4';$c = '+';$sum = $a.$c.$b;echo $sum, PHP_EOL;//可以这样echo eval("return $sum;"), PHP_EOL;//也可以这样$f = create_function('', "return $sum;");echo $f();
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感谢帮助
echo eval("return $sum;");
这段代码是有用的。
后面的那一段定义的变量f测试的时候发现出错。

拜托你抄仔细了 

$f = create_function('', "return $sum;");echo $f();
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，字符串，运算符，整型相加减。怎么写式子？
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