php一个表单中怎么删除指定行

#在需要查找的内容后一行新起一行插入内容
 function insertAfterTarget($filePath, $insertCont, $target)
 {
 $result = null;
 $fileCont = file_get_contents($filePath);
 $targetIndex = strpos($fileCont, $target); #查找目标字符串的坐标

 if ($targetIndex !== false) {
 #找到target的后一个换行符
 $chLineIndex = strpos(substr($fileCont, $targetIndex), "\n") + $targetIndex;
 if ($chLineIndex !== false) {
 #插入需要插入的内容
 $result = substr($fileCont, 0, $chLineIndex + 1) . $insertCont . "\n" . substr($fileCont, $chLineIndex + 1);
 $fp = fopen($filePath, "w+");
 fwrite($fp, $result);
 fclose($fp);
 }
 }
 }

 #删除内容所在的某一行
 function delTargetLine($filePath, $target)
 {
 $result = null;
 $fileCont = file_get_contents($filePath);
 $targetIndex = strpos($fileCont, $target); #查找目标字符串的坐标

 if ($targetIndex !== false) {
 #找到target的前一个换行符
 $preChLineIndex = strrpos(substr($fileCont, 0, $targetIndex + 1), "\n");
 #找到target的后一个换行符
 $AfterChLineIndex = strpos(substr($fileCont, $targetIndex), "\n") + $targetIndex;
 if ($preChLineIndex !== false && $AfterChLineIndex !== false) {
 #重新写入删掉指定行后的内容
 $result = substr($fileCont, 0, $preChLineIndex + 1) . substr($fileCont, $AfterChLineIndex + 1);
 $fp = fopen($filePath, "w+");
 fwrite($fp, $result);
 fclose($fp);
 }
 }
 }

 #获取某段内容的行号
 /**
 * @param $filePath
 * @param $target 待查找字段
 * @param bool $first 是否再匹配到第一个字段后退出
 * @return array
 */
 function getLineNum($filePath, $target, $first = false)
 {
 $fp = fopen($filePath, "r");
 $lineNumArr = array();
 $lineNum = 0;
 while (!feof($fp)) {
 $lineNum++;
 $lineCont = fgets($fp);
 if (strstr($lineCont, $target)) {
 if($first) {
 return $lineNum;
 } else {
 $lineNumArr[] = $lineNum;
 }
 }
 }
 return $lineNumArr;
 }