Symfony\Component\VarDumper\Dumper\HtmlDumper::getDumpHeader PHP Method

    protected function getDumpHeader()
    {
        $this->headerIsDumped = null !== $this->outputStream ? $this->outputStream : $this->lineDumper;
        if (null !== $this->dumpHeader) {
            return $this->dumpHeader;
        }
        $line = str_replace('{$options}', json_encode($this->displayOptions, JSON_FORCE_OBJECT), <<<'EOHTML'
<script>
Sfdump = window.Sfdump || (function (doc) {

var refStyle = doc.createElement('style'),
    rxEsc = /([.*+?^${}()|\[\]\/\\])/g,
    idRx = /\bsf-dump-\d+-ref[012]\w+\b/,
    keyHint = 0 <= navigator.platform.toUpperCase().indexOf('MAC') ? 'Cmd' : 'Ctrl',
    addEventListener = function (e, n, cb) {
        e.addEventListener(n, cb, false);
    };

(doc.documentElement.firstElementChild || doc.documentElement.children[0]).appendChild(refStyle);

if (!doc.addEventListener) {
    addEventListener = function (element, eventName, callback) {
        element.attachEvent('on' + eventName, function (e) {
            e.preventDefault = function () {e.returnValue = false;};
            e.target = e.srcElement;
            callback(e);
        });
    };
}

function toggle(a, recursive) {
    var s = a.nextSibling || {}, oldClass = s.className, arrow, newClass;

    if ('sf-dump-compact' == oldClass) {
        arrow = '▼';
        newClass = 'sf-dump-expanded';
    } else if ('sf-dump-expanded' == oldClass) {
        arrow = '▶';
        newClass = 'sf-dump-compact';
    } else {
        return false;
    }

    a.lastChild.innerHTML = arrow;
    s.className = newClass;

    if (recursive) {
        try {
            a = s.querySelectorAll('.'+oldClass);
            for (s = 0; s < a.length; ++s) {
                if (a[s].className !== newClass) {
                    a[s].className = newClass;
                    a[s].previousSibling.lastChild.innerHTML = arrow;
                }
            }
        } catch (e) {
        }
    }

    return true;
};

return function (root, x) {
    root = doc.getElementById(root);

    var indentRx = new RegExp('^('+(root.getAttribute('data-indent-pad') || '  ').replace(rxEsc, '\\$1')+')+', 'm'),
        options = {$options},
        elt = root.getElementsByTagName('A'),
        len = elt.length,
        i = 0, s, h,
        t = [];

    while (i < len) t.push(elt[i++]);

    for (i in x) {
        options[i] = x[i];
    }

    function a(e, f) {
        addEventListener(root, e, function (e) {
            if ('A' == e.target.tagName) {
                f(e.target, e);
            } else if ('A' == e.target.parentNode.tagName) {
                f(e.target.parentNode, e);
            } else if (e.target.nextElementSibling && 'A' == e.target.nextElementSibling.tagName) {
                f(e.target.nextElementSibling, e, true);
            }
        });
    };
    function isCtrlKey(e) {
        return e.ctrlKey || e.metaKey;
    }
    addEventListener(root, 'mouseover', function (e) {
        if ('' != refStyle.innerHTML) {
            refStyle.innerHTML = '';
        }
    });
    a('mouseover', function (a, e, c) {
        if (c) {
            e.target.style.cursor = "pointer";
        } else if (a = idRx.exec(a.className)) {
            try {
                refStyle.innerHTML = 'pre.sf-dump .'+a[0]+'{background-color: #B729D9; color: #FFF !important; border-radius: 2px}';
            } catch (e) {
            }
        }
    });
    a('click', function (a, e, c) {
        if (/\bsf-dump-toggle\b/.test(a.className)) {
            e.preventDefault();
            if (!toggle(a, isCtrlKey(e))) {
                var r = doc.getElementById(a.getAttribute('href').substr(1)),
                    s = r.previousSibling,
                    f = r.parentNode,
                    t = a.parentNode;
                t.replaceChild(r, a);
                f.replaceChild(a, s);
                t.insertBefore(s, r);
                f = f.firstChild.nodeValue.match(indentRx);
                t = t.firstChild.nodeValue.match(indentRx);
                if (f && t && f[0] !== t[0]) {
                    r.innerHTML = r.innerHTML.replace(new RegExp('^'+f[0].replace(rxEsc, '\\$1'), 'mg'), t[0]);
                }
                if ('sf-dump-compact' == r.className) {
                    toggle(s, isCtrlKey(e));
                }
            }

            if (c) {
            } else if (doc.getSelection) {
                try {
                    doc.getSelection().removeAllRanges();
                } catch (e) {
                    doc.getSelection().empty();
                }
            } else {
                doc.selection.empty();
            }
        } else if (/\bsf-dump-str-toggle\b/.test(a.className)) {
            e.preventDefault();
            e = a.parentNode.parentNode;
            e.className = e.className.replace(/sf-dump-str-(expand|collapse)/, a.parentNode.className);
        }
    });

    elt = root.getElementsByTagName('SAMP');
    len = elt.length;
    i = 0;

    while (i < len) t.push(elt[i++]);
    len = t.length;

    for (i = 0; i < len; ++i) {
        elt = t[i];
        if ('SAMP' == elt.tagName) {
            elt.className = 'sf-dump-expanded';
            a = elt.previousSibling || {};
            if ('A' != a.tagName) {
                a = doc.createElement('A');
                a.className = 'sf-dump-ref';
                elt.parentNode.insertBefore(a, elt);
            } else {
                a.innerHTML += ' ';
            }
            a.title = (a.title ? a.title+'\n[' : '[')+keyHint+'+click] Expand all children';
            a.innerHTML += '<span>▼</span>';
            a.className += ' sf-dump-toggle';
            x = 1;
            if ('sf-dump' != elt.parentNode.className) {
                x += elt.parentNode.getAttribute('data-depth')/1;
            }
            elt.setAttribute('data-depth', x);
            if (x > options.maxDepth) {
                toggle(a);
            }
        } else if ('sf-dump-ref' == elt.className && (a = elt.getAttribute('href'))) {
            a = a.substr(1);
            elt.className += ' '+a;

            if (/[\[{]$/.test(elt.previousSibling.nodeValue)) {
                a = a != elt.nextSibling.id && doc.getElementById(a);
                try {
                    s = a.nextSibling;
                    elt.appendChild(a);
                    s.parentNode.insertBefore(a, s);
                    if (/^[@#]/.test(elt.innerHTML)) {
                        elt.innerHTML += ' <span>▶</span>';
                    } else {
                        elt.innerHTML = '<span>▶</span>';
                        elt.className = 'sf-dump-ref';
                    }
                    elt.className += ' sf-dump-toggle';
                } catch (e) {
                    if ('&' == elt.innerHTML.charAt(0)) {
                        elt.innerHTML = '…';
                        elt.className = 'sf-dump-ref';
                    }
                }
            }
        }
    }

    if (0 >= options.maxStringLength) {
        return;
    }
    try {
        elt = root.querySelectorAll('.sf-dump-str');
        len = elt.length;
        i = 0;
        t = [];

        while (i < len) t.push(elt[i++]);
        len = t.length;

        for (i = 0; i < len; ++i) {
            elt = t[i];
            s = elt.innerText || elt.textContent;
            x = s.length - options.maxStringLength;
            if (0 < x) {
                h = elt.innerHTML;
                elt[elt.innerText ? 'innerText' : 'textContent'] = s.substring(0, options.maxStringLength);
                elt.className += ' sf-dump-str-collapse';
                elt.innerHTML = '<span class=sf-dump-str-collapse>'+h+'<a class="sf-dump-ref sf-dump-str-toggle" title="Collapse"> ◀</a></span>'+
                    '<span class=sf-dump-str-expand>'+elt.innerHTML+'<a class="sf-dump-ref sf-dump-str-toggle" title="'+x+' remaining characters"> ▶</a></span>';
            }
        }
    } catch (e) {
    }
};

})(document);
</script><style>
pre.sf-dump {
    display: block;
    white-space: pre;
    padding: 5px;
}
pre.sf-dump span {
    display: inline;
}
pre.sf-dump .sf-dump-compact {
    display: none;
}
pre.sf-dump abbr {
    text-decoration: none;
    border: none;
    cursor: help;
}
pre.sf-dump a {
    text-decoration: none;
    cursor: pointer;
    border: 0;
    outline: none;
    color: inherit;
}
pre.sf-dump .sf-dump-ellipsis {
    display: inline-block;
    overflow: visible;
    text-overflow: ellipsis;
    max-width: 5em;
    white-space: nowrap;
    overflow: hidden;
    vertical-align: top;
}
pre.sf-dump code {
    display:inline;
    padding:0;
    background:none;
}
.sf-dump-str-collapse .sf-dump-str-collapse {
    display: none;
}
.sf-dump-str-expand .sf-dump-str-expand {
    display: none;
}
EOHTML
);
        foreach ($this->styles as $class => $style) {
            $line .= 'pre.sf-dump' . ('default' === $class ? ', pre.sf-dump' : '') . ' .sf-dump-' . $class . '{' . $style . '}';
        }
        return $this->dumpHeader = preg_replace('/\\s+/', ' ', $line) . '</style>' . $this->dumpHeader;
    }