FormIt set value in textarea using $hook->setValue('message','bla.....');

<textarea name="message" id="message" cols="55" rows="7" value="[[!+fi.text]]">[[!+fi.text]]</textarea>

<?php
$hook->setValue('message','bla....');
return true;

[[!FormIt? &validate= `kennwort:required,
                       text:required:stripTags,
                       startWarn:regexp=^/[0-9]{2}[\/][0-9]{4}[zZ]/^,
                       endWarn:regexp=^/[0-9]{2}[\/][0-9]{4}[zZ]/^,
                       issued:regexp=^/[0-9]{2}[\/][0-9]{4}[zZ]/^,
                       lfdNr:regexp=^/[0-9]{2}/^`
           &clearFieldsOnSuccess= `0`
           &preHooks= `loadWarnformParam`
           &hooks=    `warnForm`
]]

[[!+fi.validation_error_message:notempty=`<p>[[!+fi.validation_error_message]]</p>`]]

<form action="[[~[[*id]]]]" method="post" class="form">
    <section>
        <fieldset>
            <legend>Inhalt:</legend>
                <div>
                    <label for="kennwort"> Kennwort: <span class="error">[[!+fi.error.kennwort]]</span></label>
                    <input type="text" name="kennwort" id="kennwort" placeholder="Gewitter, Wind, Starkniederschlag etc." value="[[!+fi.kennwort]]">
                </div>
                <div id="warntext>
                    <label for="text"> Warntext: <span class="error">[[!+fi.error.text]]</span></label>
                    <textarea name="text" id="text" cols="50" rows="3" placeholder="Bitte Warntext eingeben..." value="[[!+fi.text]]" />[[fi.text]]</textarea>
                </div>
                <div>
                    <label for="startWarn"> gültig von: <span class="error">[[!+fi.error.startWarn]]</span></label>
                    <input type="text" name="startWarn" id="startWarn" placeholder="15/0800Z" value="[[!+fi.startWarn]]">
                </div>
                <div>
                    <label for="endWarn"> bis: <span class="error">[[!+fi.error.endWarn]]</span></label>
                    <input type="text" name="endWarn" id="endWarn" placeholder="15/2200Z" value="[[!+fi.endWarn]]">
                </div>
                <div>
                    <label for="issued"> herausgegeben am: <span class="error">[[!+fi.error.endWarn]]</span></label>
                    <input type="text" name="issued" id="issued" value="[[!+fi.issued]]">
                </div>
                <div>
                    <label for="lfdNr"> ETMN Nr: <span class="error">[[!+fi.error.lfdNr]]</span></label>
                    <input type="text" name="lfdNr" id="lfdNr" placeholder="01" value="[[!+fi.lfdNr]]">
                </div>
                <div>
                    <label for="chngcncl"> Aufhebung/Änderung: <span class="error">[[!+fi.error.chngcncl]]</span></label>
                    <input type="text" name="chngcncl" id="chngcncl" placeholder="Aufhebung Nr.XX/Änderung Nr. XX" value="[[!+fi.chngcncl]]">
                </div>
        </fieldset>
        <div class="form-buttons">
            <input type="submit" value="Warnung erstellen">
        </div>
    </section>
</form>

<?php
$fp = fopen("images/geomops1/Warnung_nicht_loeschen.txt","r");
$i = 0;
if($fp){
    while(!feof($fp)){
       $zeile[$i] = fgets($fp);
       $i++;
    }
    fclose($fp);
    $hook->setValue('kennwort', substr($zeile[0],3));
    $hook->setValue('text', substr($zeile[1], 3));
    $hook->setValue('startWarn', substr($zeile[2], 15, 8));
    $hook->setValue('endWarn', substr($zeile[2], 28, 8));
    if (strlen($zeile[4]) !== 0) {
        $hook->setValue('issued', substr($zeile[4], 14, 8));
    } else {
        $timestamp = time();
        $datum = date("d/Hi", $timestamp) . "Z";
        $hook->setValue('issued',$datum);
    }
    $hook->setValue('lfdNr', substr($zeile[5], 12, 2));
}  
else {
    $modx->log(xPDO::LOG_LEVEL_ERROR,'unable to open $Bulletin');
    print "Datei $Bulletin nicht gefunden<br>";
    $timestamp = time();
    $datum = date("d/Hi", $timestamp) . "Z";
    $hook->setValue('issued',$datum);
}
return true;

<?php
$hook=$scriptProperties['hook'];
$kennwort = $hook->getValue('kennwort');
$warntext = $hook->getValue('text');
$startWarn = $hook->getValue('startWarn');
if (stristr($startWarn, "Z") === FALSE) {
    $startWarn = $startWarn . "Z";
}
$endWarn = $hook->getValue('endWarn');
if (stristr($endWarn, "Z") === FALSE) {
    $endWarn = $endWarn . "Z";
}
$issued = $hook->getValue('issued');
if (stristr($issued, "Z") === FALSE) {
    $issued = $issued . "Z";
}
$lfdNr = $hook->getValue('lfdNr');
$chngcncl = $hook->getValue('chngcncl');
if (strlen($chngcncl) > 0) {
    $chngcncl = "\r\n" . "7. " . $chngcncl;
} else {
    $chngcncl = "";
}
$sign = $hook->getValue('sign');
$check = "cancel";
if (strcasecmp($warntext, "cancel") !== 0) {
    $text = "1. " . $kennwort . "\r\n" . "2. " . $warntext . "\r\n" . "3. Gültig von " . $startWarn . " bis " . $endWarn . "\r\n" . "4. ETMN und Umgebung " . "\r\n" . "5. ausgegeben " . $issued . "\r\n" . "6. ETMN Nr. " . $lfdNr . $chngcncl;
} else {
    $text="";
}
$myfile = fopen("images/geomops1/Warnung_nicht_loeschen.txt", "w") or $modx->log(xPDO::LOG_LEVEL_ERROR, 'unable to write warn message');

fwrite($myfile, $text);
fclose($myfile);

return true;  //<-- if you omit this or return false, your form won't validate