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13 years ago
I needed to stream a txt file (here big xml file) to get nodes blockwise. I couldn't find a shorter way. So i did write this class.

Function: streams a complete file and returns the content between two search strings with their search strings (multi byte safe)

Hope it helps anyone.

PS: It lacks any boolean checks / exception handling for non existing files / read errors.

<?php
/**
 * Reads txt-files blockwise
 * Usage:
    $c_streamFileTxt = new streamFileTxt;
    $_args = array(

        'file' => 'temporary.xml',
        'start_string' => '<Product>',
        'stop_string' => '</Product>',
        'block_size' => '8192'
    );
    
    $c_streamFileTxt->setArgs($_args);

    while ($txt_block = $c_streamFileTxt->getNextBlock())
    {
        // use $txt_block for something
    }
 */

class streamFileTxt
{
    private $handle;
    private $file;
    private $file_offset;
    private $block;
    private $start_string;
    private $stop_string;
    private $block_size;

    /**
     * Sett class arguments
     * @param array $_args
     */
    public function setArgs($_args)
    {
        $this->file = $_args['file'];
        $this->start_string = $_args['start_string'];
        $this->stop_string = $_args['stop_string'];
        $this->block_size = $_args['block_size'];
    }

    /**
     * Get next textblock within a file
     * @param void
     * @return string $textblock
     */
    public function getNextBlock()
    {
        $this->openFile();

        fseek($this->handle, $this->file_offset);
        $start_string_found = false;
        $stop_string_found = false;
        while (!feof($this->handle))
        {
            $txt_block = fread($this->handle, $this->block_size);

            if (!$start_string_found) // while not start start snippet found
            {
                $strpos = mb_strpos($txt_block, $this->start_string);
                if ($strpos !== false)
                {
                    // cut of first left chunk
                    $txt_block = mb_substr($txt_block, $strpos, $this->block_size);
                    $start_string_found = true;
                }
            }

            if ($start_string_found && !$stop_string_found) // start snipped found, looking for stop snippet
            { 
                $strpos = mb_strpos($txt_block, $this->stop_string);
                if ($strpos !== false)
                {
                    $removed_block_size = mb_strlen($txt_block) - $strpos;
                    $txt_block = mb_substr($txt_block, 0, $strpos + mb_strlen($this->stop_string)); 
                    $stop_string_found = true;
                    $this->setFileOffset($removed_block_size);
                }
            }

            if ($stop_string_found) // stop-snippet found, keep file offset, return 
            {
                $this->closeFile();
                return $txt_block;
            }
        }

        $this->closeFile();
        return false;
    }
    
    /**
     * Set current file offset and consider the removed block size
     * current file position = current file offset - removed block size
     * @param int $removed_block_size
     */
    private function setFileOffset($removed_block_size)
    {
        $this->file_offset = ftell($this->handle) - $removed_block_size;
    }
    
    /**
     * close current file
     * @param void
     * @return void
     */
    private function openFile()
    {
        $this->handle = fopen($this->file, 'r');
    }
    
    /**
     * open file
     * @param void
     * @return void
     */
    private function closeFile()
    {
        fclose($this->handle);
    }
}
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