This time I will bring you a detailed explanation of the steps to use the PHP generator. What are the precautions when using the PHP generator? Here are practical cases, let’s take a look.
1. Official description: Generators provide an easier way to implement simple object iteration. Compared with defining a class to implement the Iterator interface, the performance overhead and complexity are much greater. reduce. Generators allow you to write code in a foreach block to iterate over a set of data without creating an array in memory.
2. The generator is just like an ordinary custom function. Different from the ordinary function that only returns once, the generator can yield as many times as needed to generate the iteration that needs to be value.
3. Code example:
//未使用生成器 echo '开始内存:'.getMemory().'<br>'; $nums = range(0,1000000); echo '结束内存:'.getMemory().'<br>'; //输出结果 //开始内存:0.23M //结束内存:130.31 //使用生成器 echo '开始内存:'.getMemory().'<br>'; $nums = xrange(1000000); function xrange($total) { for ($i = 0; $i '; //输出结果 //开始内存:0.23M //结束内存:0.23M
4. Practical application example
/** * 大量数据生成示例 * @param int $page * @param int $limit * @return Generator */ public function generator($page = 1,$limit = 50000) { while (true) { echo "第{$page}次".'generator开始内存:'.$this->getMemory().'<br>'; $start = ($page-1) * $limit; $sql = "SELECT p.id,p.wh_code,p.goods_sn FROM p_product as p WHERE p.wh_code LIKE '%YB%' OR p.wh_code LIKE '%DZWH%' LIMIT {$start},{$limit} "; $resultAll = db()->fetchAll($sql); yield $resultAll; //生成器 if (count($resultAll) != $limit) { break; } echo "第{$page}次".'generator结束内存:'.$this->getMemory().'<br>'; $page++; } } //测试生成器内存消耗 // foreach ($this->generator() as $result) { // var_dump($result[0]); // }
I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other php Chinese websites related articles!
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The above is the detailed content of Detailed explanation of steps to use PHP generator. For more information, please follow other related articles on the PHP Chinese website!

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。


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