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php如何实现预览功能

2026-01-29 04:17:39PHP

文件上传预览

在PHP中实现文件上传预览功能，可以通过前端JavaScript结合后端处理实现。前端使用FileReader读取文件内容，后端接收并处理文件数据。

前端HTML部分：

<input type="file" id="fileInput" accept="image/*">
<img id="preview" style="max-width: 300px; display: none;">

JavaScript部分：

document.getElementById('fileInput').addEventListener('change', function(e) {
    const file = e.target.files[0];
    const reader = new FileReader();

    reader.onload = function(event) {
        document.getElementById('preview').src = event.target.result;
        document.getElementById('preview').style.display = 'block';
    };

    reader.readAsDataURL(file);
});

PHP后端接收文件：

if ($_SERVER['REQUEST_METHOD'] === 'POST' && isset($_FILES['file'])) {
    $uploadDir = 'uploads/';
    $uploadFile = $uploadDir . basename($_FILES['file']['name']);

    if (move_uploaded_file($_FILES['file']['tmp_name'], $uploadFile)) {
        echo "File uploaded successfully.";
    } else {
        echo "File upload failed.";
    }
}

图片缩略图生成

对于图片预览，可以使用PHP的GD库生成缩略图：

function createThumbnail($sourcePath, $targetPath, $maxWidth, $maxHeight) {
    list($sourceWidth, $sourceHeight, $sourceType) = getimagesize($sourcePath);

    switch ($sourceType) {
        case IMAGETYPE_GIF:
            $sourceImage = imagecreatefromgif($sourcePath);
            break;
        case IMAGETYPE_JPEG:
            $sourceImage = imagecreatefromjpeg($sourcePath);
            break;
        case IMAGETYPE_PNG:
            $sourceImage = imagecreatefrompng($sourcePath);
            break;
    }

    $ratio = min($maxWidth/$sourceWidth, $maxHeight/$sourceHeight);
    $newWidth = $sourceWidth * $ratio;
    $newHeight = $sourceHeight * $ratio;

    $thumbnail = imagecreatetruecolor($newWidth, $newHeight);
    imagecopyresampled($thumbnail, $sourceImage, 0, 0, 0, 0, $newWidth, $newHeight, $sourceWidth, $sourceHeight);

    imagejpeg($thumbnail, $targetPath);
    imagedestroy($sourceImage);
    imagedestroy($thumbnail);
}

PDF文档预览

使用第三方库如TCPDF或mPDF可以生成PDF预览：

require_once('tcpdf/tcpdf.php');

$pdf = new TCPDF();
$pdf->AddPage();
$pdf->SetFont('helvetica', 'B', 16);
$pdf->Cell(0, 10, 'PDF Preview', 0, 1, 'C');
$pdf->Output('preview.pdf', 'I');

视频预览截图

使用FFmpeg从视频中提取缩略图：

$videoPath = 'video.mp4';
$thumbnailPath = 'thumbnail.jpg';
$ffmpegCommand = "ffmpeg -i {$videoPath} -ss 00:00:01 -vframes 1 {$thumbnailPath}";
exec($ffmpegCommand);

数据库内容预览

对于从数据库检索的内容，可以在展示前进行截断处理：

function previewText($text, $length = 100) {
    if (strlen($text) > $length) {
        $text = substr($text, 0, $length) . '...';
    }
    return $text;
}

php如何实现预览功能