--prefix=/usr/local/php7 --with-config-file-path=/usr/local/php7/etc --enable-fpm --with-fpm-user=www --with-fpm-group=www --with-mysqli --with-pdo-mysql --with-iconv-dir --with-freetype-dir --with-jpeg-dir --with-png-dir --with-zlib --with-libxml-dir=/usr --enable-xml --disable-rpath --enable-bcmath --enable-shmop --enable-sysvsem --enable-inline-optimization --with-curl --enable-mbregex --enable-mbstring --with-mcrypt --enable-ftp --with-gd --enable-gd-native-ttf --with-openssl --with-mhash --enable-pcntl --enable-sockets --with-xmlrpc --enable-zip --enable-soap --without-pear --with-gettext --disable-fileinfo --enable-maintainer-zts

ln -s /usr/local/php7/bin/php /usr/bin/php7
ln -s /usr/local/php7/bin/php-config /usr/bin/php7-config 
ln -s /usr/local/php7/bin/phpize /usr/bin/php7ize
ln -s /usr/local/php7/sbin/php-fpm /usr/sbin/php7-fpm

[root@localhost test]# php7 -v
PHP 7.0.0 (cli) (built: Dec 2 2015 19:19:14) ( ZTS )
Copyright (c) 1997-2015 The PHP Group
Zend Engine v3.0.0, Copyright (c) 1998-2015 Zend Technologies

<?php
$a = array();
for($i=0;$i<600000;$i++){
  $a[$i] = $i;
}
foreach($a as $i)
{
 array_key_exists($i, $a);
}

[root@localhost test]# time php search_by_key.php 
real 0m0.389s
user 0m0.337s
sys  0m0.051s
[root@localhost test]# time php search_by_key.php 
real 0m0.378s
user 0m0.308s
sys  0m0.062s
[root@localhost test]# time php search_by_key.php 
real 0m0.378s
user 0m0.317s
sys  0m0.061s

[root@localhost php7]# time php7 search_by_key.php
real 0m0.082s
user 0m0.066s
sys  0m0.014s
[root@localhost php7]# time php7 search_by_key.php
real 0m0.080s
user 0m0.058s
sys  0m0.021s
[root@localhost php7]# time php7 search_by_key.php
real 0m0.080s
user 0m0.053s
sys  0m0.026s`

<?php
$a = array();
for($i=0;$i<600000;$i++){
  $a[$i] = $i;
}
foreach($a as $i)
{
 array_key_exists($i, $a);
}
[root@localhost test]# time php search_by_val.php 
real 0m24.296s
user 0m24.184s
sys  0m0.025s
[root@localhost test]# time php search_by_val.php 
real 0m25.523s
user 0m25.317s
sys  0m0.026s
[root@localhost test]# time php search_by_val.php 
real 0m26.026s
user 0m25.478s
sys  0m0.092s

[root@localhost php7]# time php7 search_by_val.php
real 0m3.362s
user 0m3.323s
sys  0m0.007s
[root@localhost php7]# time php7 search_by_val.php
real 0m3.266s
user 0m3.251s
sys  0m0.004s
[root@localhost php7]# time php7 search_by_val.php
real 0m3.290s
user 0m3.275s
sys  0m0.006s

[root@localhost php7]# time php7 prime_v3.php 2000000
real 0m1.151s
user 0m1.129s
sys  0m0.010s
[root@localhost php7]# time php7 prime_v3.php 2000000
real 0m1.141s
user 0m1.123s
sys  0m0.011s
[root@localhost php7]# time php7 prime_v3.php 2000000
real 0m1.145s
user 0m1.128s
sys  0m0.010s`

[root@localhost test]# time php prime_v3.php 2000000
prime number count under 2000000 is :148933
real 0m4.425s
user 0m4.380s
sys  0m0.023s
[root@localhost test]# time php prime_v3.php 2000000
prime number count under 2000000 is :148933
real 0m4.457s
user 0m4.414s
sys  0m0.032s
[root@localhost test]# time php prime_v3.php 2000000
prime number count under 2000000 is :148933
real 0m4.464s
user 0m4.399s
sys  0m0.046s

<?php
/* 
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
$num = $argv[1];
$ret = array(2);
$flag = false;
for($i=3; $i<=$num; $i+=2)
{
 $flag = false;
 $sqrt = sqrt($i);
 foreach($ret as $prime)
 {
  if($i%$prime == 0)
  {
   $flag = true;
   break;
  }
  if($prime>$sqrt)
  {
   break;
  }
 }
 if(!$flag)
 {
  $ret[] = $i;
 }
}
echo (count($ret))."\n";