PHP如何正则表达式获取SQL语句中的表名？

有一个SQL语句集合，里面可能有select、select ... left join、update、delete、insert。

要从这语句集合中获取到所有的表名，代码如下:

<?php function get_sql_tables($sqlString) {     $sqlString = str_replace( '`','',trim($sqlString) ).' AND 1=1 ';     $key = strtolower(substr($sqlString, 0, 6));     if( $key === 'select' ){         $tmp = explode('where' , strtolower( trim( $sqlString ) ) );         $tmp = explode('from',$tmp[0]);         if ( strpos($tmp[1],',') !== false && ! stristr( $tmp[1],'select')){             $tmp = explode( ',' , $tmp[1] );             foreach( $tmp as $k => $v ){                 $v = trim( $v );                 if( strpos( $v , ' ') !== false ){                     $tv = explode(' ' , $v);                     $return[] = $tv[0];                 }             }             return $return;         }else{             $expression = '/((SELECT.+?FROM)|(LEFT\s+JOIN|JOIN|LEFT))[\s`]+?(\w+)[\s`]+?/is';         }     }else if( $key === 'delete' ){         $expression = '/DELETE\s+?FROM[\s`]+?(\w+)[\s`]+?/is';     }else if( $key === 'insert' ){         $expression = '/INSERT\s+?INTO[\s`]+?(\w+)[\s`]+?/is';     }else if( $key === 'update' ){         $tmp = explode( 'set' , strtolower( str_replace('`','',trim( $sqlString ) ) ) );         $tmp = explode( 'update' , $tmp[0] );         if ( strpos($tmp[1] , ',' ) !== false && ! stristr( $tmp[1] , 'update' ) ){             $tmp = explode( ',' , $tmp[1] );             foreach( $tmp as $k => $v ){                 $v = trim( $v );                 if( strpos( $v , ' ') !== false ){                     $tv = explode(' ' , $v);                     $return[] = $tv[0];                 }             }             return $return;         }else{             $expression = '/UPDATE[\s`]+?(\w+)[\s`]+?/is';         }     }     preg_match_all($expression, $sqlString, $matches);     return array_unique(array_pop($matches)); }

使用姿势：

<?php $sql = "select count(*) as count from order as a left join user as b on a.user_id = b.user_id where a.title like '%老季%'"; var_dump(get_sql_tables());#输出结果：order和user  $sql = "select * from T_5 a, T_6 b , T_7 c where a.id=b.id"; var_dump(get_sql_tables());#输出结果：Array ( [0] => T_5 [1] => T_6 [2] => T_7 )